D-Link DFL-210 - NetDefend - Security Appliance User manual

Network Security Solution http://www.dlink.com
Security
Security
DFL-210/ 800/1600/ 2500
DFL-260/ 860/1660/ 2560(G)
Ver 2.26.01
Network Security Firewall
User Manual

User Manual
DFL-210/260/800/860/1600/1660/2500/2560/2560G
NetDefendOS Version 2.26.01
D-Link Corporation
No. 289, Sinhu 3rd Rd, Neihu District, Taipei City 114, Taiwan R.O.C.
http://www.DLink.com
Published 2010-01-11

User Manual
DFL-210/260/800/860/1600/1660/2500/2560/2560G
NetDefendOS Version 2.26.01
Published 2010-01-11
Copyright Notice
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international copyright laws, with all rights reserved. Neither this manual, nor any of the material
contained herein, may be reproduced without the written consent of D-Link.
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D-LINK WILL NOT BE LIABLE FOR THIRD-PARTY CLAIMS AGAINST CUSTOMER FOR
LOSSES OR DAMAGES. D-LINK WILL IN NO EVENT BE LIABLE FOR ANY DAMAGES IN
EXCESS OF THE AMOUNT D-LINK RECEIVED FROM THE END-USER FOR THE
PRODUCT.

Table of Contents
Preface ...............................................................................................................13
1. NetDefendOS Overview ....................................................................................15
1.1. Features ................................................................................................15
1.2. NetDefendOS Architecture ......................................................................18
1.2.1. State-based Architecture ...............................................................18
1.2.2. NetDefendOS Building Blocks .......................................................18
1.2.3. Basic Packet Flow ........................................................................19
1.3. NetDefendOS State Engine Packet Flow .....................................................21
2. Management and Maintenance ............................................................................26
2.1. Managing NetDefendOS ..........................................................................26
2.1.1. Overview ...................................................................................26
2.1.2. The Default Administrator Account .................................................27
2.1.3. The Web Interface .......................................................................27
2.1.4. The CLI .....................................................................................31
2.1.5. CLI Scripts .................................................................................39
2.1.6. Secure Copy ...............................................................................42
2.1.7. The Console Boot Menu ...............................................................45
2.1.8. Management Advanced Settings .....................................................46
2.1.9. Working with Configurations .........................................................47
2.2. Events and Logging ................................................................................53
2.2.1. Overview ...................................................................................53
2.2.2. Log Messages .............................................................................53
2.2.3. Log Message Distribution ..............................................................54
2.2.4. Advanced Log Settings .................................................................56
2.3. RADIUS Accounting ..............................................................................58
2.3.1. Overview ...................................................................................58
2.3.2. RADIUS Accounting Messages ......................................................58
2.3.3. Interim Accounting Messages ........................................................60
2.3.4. Activating RADIUS Accounting .....................................................60
2.3.5. RADIUS Accounting Security ........................................................60
2.3.6. RADIUS Accounting and High Availability ......................................60
2.3.7. Handling Unresponsive Servers ......................................................61
2.3.8. Accounting and System Shutdowns .................................................61
2.3.9. Limitations with NAT ...................................................................61
2.3.10. RADIUS Advanced Settings ........................................................61
2.4. Hardware Monitoring ..............................................................................63
2.5. SNMP Monitoring ..................................................................................65
2.5.1. SNMP Advanced Settings .............................................................66
2.6. The pcapdump Command ........................................................................68
2.7. Maintenance ..........................................................................................71
2.7.1. Auto-Update Mechanism ...............................................................71
2.7.2. Creating Backup Files ...................................................................71
2.7.3. Restore to Factory Defaults ............................................................72
3. Fundamentals ...................................................................................................75
3.1. The Address Book ..................................................................................75
3.1.1. Overview ...................................................................................75
3.1.2. IP Addresses ...............................................................................75
3.1.3. Ethernet Addresses .......................................................................77
3.1.4. Address Groups ...........................................................................78
3.1.5. Auto-Generated Address Objects ....................................................78
3.1.6. Address Book Folders ...................................................................79
3.2. Services ................................................................................................80
3.2.1. Overview ...................................................................................80
3.2.2. TCP and UDP Based Services ........................................................81
3.2.3. ICMP Services ............................................................................83
3.2.4. Custom IP Protocol Services ..........................................................84
3.2.5. Service Groups ............................................................................85
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3.3. Interfaces ..............................................................................................86
3.3.1. Overview ...................................................................................86
3.3.2. Ethernet Interfaces .......................................................................87
3.3.3. VLAN .......................................................................................92
3.3.4. PPPoE .......................................................................................95
3.3.5. GRE Tunnels ..............................................................................97
3.3.6. Interface Groups ........................................................................100
3.4. ARP ..................................................................................................102
3.4.1. Overview .................................................................................102
3.4.2. ARP in NetDefendOS .................................................................102
3.4.3. ARP Cache ...............................................................................102
3.4.4. Static and Published ARP Entries ..................................................104
3.4.5. Using ARP Advanced Settings .....................................................105
3.4.6. ARP Advanced Settings Summary ................................................106
3.5. The IP Rule Set ....................................................................................109
3.5.1. Security Policies ........................................................................109
3.5.2. IP Rule Evaluation .....................................................................111
3.5.3. IP Rule Actions .........................................................................112
3.5.4. Editing IP rule set Entries ............................................................113
3.5.5. IP Rule Set Folders ....................................................................113
3.6. Schedules ...........................................................................................115
3.7. Certificates .........................................................................................117
3.7.1. Overview .................................................................................117
3.7.2. Certificates in NetDefendOS ........................................................118
3.7.3. CA Certificate Requests ..............................................................119
3.8. Date and Time .....................................................................................121
3.8.1. Overview .................................................................................121
3.8.2. Setting Date and Time ................................................................121
3.8.3. Time Servers ............................................................................122
3.8.4. Settings Summary for Date and Time ............................................125
3.9. DNS ..................................................................................................128
4. Routing .........................................................................................................131
4.1. Overview ............................................................................................131
4.2. Static Routing ......................................................................................132
4.2.1. The Principles of Routing ............................................................132
4.2.2. Static Routing ...........................................................................136
4.2.3. Route Failover ..........................................................................140
4.2.4. Host Monitoring for Route Failover ...............................................142
4.2.5. Proxy ARP ...............................................................................145
4.3. Policy-based Routing ............................................................................146
4.3.1. Overview .................................................................................146
4.3.2. Policy-based Routing Tables ........................................................146
4.3.3. Policy-based Routing Rules .........................................................146
4.3.4. Routing Table Selection ..............................................................147
4.3.5. The Ordering parameter ..............................................................147
4.4. Route Load Balancing ...........................................................................151
4.5. Dynamic Routing .................................................................................157
4.5.1. Dynamic Routing overview .........................................................157
4.5.2. OSPF ......................................................................................158
4.5.3. Dynamic Routing Policy .............................................................162
4.6. Multicast Routing .................................................................................165
4.6.1. Overview .................................................................................165
4.6.2. Multicast Forwarding with SAT Multiplex Rules .............................165
4.6.3. IGMP Configuration ..................................................................169
4.6.4. Advanced IGMP Settings ............................................................174
4.7. Transparent Mode ................................................................................177
4.7.1. Overview .................................................................................177
4.7.2. Enabling Internet Access .............................................................181
4.7.3. Transparent Mode Scenarios ........................................................183
4.7.4. Spanning Tree BPDU Support ......................................................187
4.7.5. Advanced Settings for Transparent Mode ....................................... 188
5. DHCP Services ..............................................................................................192
5.1. Overview ............................................................................................192
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5.2. DHCP Servers .....................................................................................193
5.3. Static DHCP Assignment .......................................................................196
5.3.1. DHCP Advanced Settings ............................................................196
5.4. DHCP Relaying ...................................................................................198
5.4.1. DHCP Relay Advanced Settings ...................................................199
5.5. IP Pools ..............................................................................................201
6. Security Mechanisms .......................................................................................204
6.1. Access Rules .......................................................................................204
6.1.1. Overview .................................................................................204
6.1.2. IP Spoofing ..............................................................................204
6.1.3. Access Rule Settings ..................................................................205
6.2. ALGs .................................................................................................207
6.2.1. Overview .................................................................................207
6.2.2. The HTTP ALG ........................................................................208
6.2.3. The FTP ALG ...........................................................................211
6.2.4. The TFTP ALG .........................................................................217
6.2.5. The SMTP ALG ........................................................................218
6.2.6. The POP3 ALG .........................................................................227
6.2.7. The PPTP ALG .........................................................................227
6.2.8. The SIP ALG ............................................................................229
6.2.9. The H.323 ALG ........................................................................239
6.2.10. The TLS ALG .........................................................................252
6.3. Web Content Filtering ...........................................................................255
6.3.1. Overview .................................................................................255
6.3.2. Active Content Handling .............................................................255
6.3.3. Static Content Filtering ...............................................................256
6.3.4. Dynamic Web Content Filtering ...................................................258
6.4. Anti-Virus Scanning .............................................................................272
6.4.1. Overview .................................................................................272
6.4.2. Implementation .........................................................................272
6.4.3. Activating Anti-Virus Scanning ....................................................273
6.4.4. The Signature Database ..............................................................274
6.4.5. Subscribing to the D-Link Anti-Virus Service ................................. 274
6.4.6. Anti-Virus Options .....................................................................274
6.5. Intrusion Detection and Prevention ..........................................................278
6.5.1. Overview .................................................................................278
6.5.2. IDP Availability for D-Link Models ..............................................278
6.5.3. IDP Rules .................................................................................280
6.5.4. Insertion/Evasion Attack Prevention ..............................................281
6.5.5. IDP Pattern Matching .................................................................282
6.5.6. IDP Signature Groups .................................................................283
6.5.7. IDP Actions ..............................................................................285
6.5.8. SMTP Log Receiver for IDP Events ..............................................285
6.6. Denial-of-Service Attack Prevention ........................................................289
6.6.1. Overview .................................................................................289
6.6.2. DoS Attack Mechanisms .............................................................289
6.6.3. Ping of Death and Jolt Attacks .....................................................289
6.6.4. Fragmentation overlap attacks: Teardrop, Bonk, Boink and Nestea ......290
6.6.5. The Land and LaTierra attacks .....................................................290
6.6.6. The WinNuke attack ...................................................................290
6.6.7. Amplification attacks: Smurf, Papasmurf, Fraggle ...........................291
6.6.8. TCP SYN Flood Attacks .............................................................292
6.6.9. The Jolt2 Attack ........................................................................292
6.6.10. Distributed DoS Attacks ............................................................292
6.7. Blacklisting Hosts and Networks .............................................................294
7. Address Translation ........................................................................................297
7.1. Overview ............................................................................................297
7.2. NAT ..................................................................................................298
7.3. NAT Pools ..........................................................................................303
7.4. SAT ...................................................................................................306
7.4.1. Translation of a Single IP Address (1:1) .........................................306
7.4.2. Translation of Multiple IP Addresses (M:N) ....................................310
7.4.3. All-to-One Mappings (N:1) .........................................................312
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7.4.4. Port Translation .........................................................................313
7.4.5. Protocols Handled by SAT ..........................................................313
7.4.6. Multiple SAT Rule Matches .........................................................313
7.4.7. SAT and FwdFast Rules ..............................................................314
8. User Authentication ........................................................................................317
8.1. Overview ............................................................................................317
8.2. Authentication Setup .............................................................................319
8.2.1. Setup Summary .........................................................................319
8.2.2. The Local Database ....................................................................319
8.2.3. External RADIUS Servers ...........................................................319
8.2.4. External LDAP Servers ...............................................................320
8.2.5. Authentication Rules ..................................................................326
8.2.6. Authentication Processing ...........................................................328
8.2.7. HTTP Authentication .................................................................328
8.3. Customizing HTML Pages .....................................................................333
9. VPN .............................................................................................................337
9.1. Overview ............................................................................................337
9.1.1. VPN Usage ...............................................................................337
9.1.2. VPN Encryption ........................................................................338
9.1.3. VPN Planning ...........................................................................338
9.1.4. Key Distribution ........................................................................339
9.1.5. The TLS Alternative for VPN ......................................................339
9.2. VPN Quick Start ..................................................................................341
9.2.1. IPsec LAN to LAN with Pre-shared Keys .......................................342
9.2.2. IPsec LAN to LAN with Certificates .............................................343
9.2.3. IPsec Roaming Clients with Pre-shared Keys ..................................344
9.2.4. IPsec Roaming Clients with Certificates .........................................346
9.2.5. L2TP Roaming Clients with Pre-Shared Keys ................................. 347
9.2.6. L2TP Roaming Clients with Certificates ........................................348
9.2.7. PPTP Roaming Clients ...............................................................349
9.3. IPsec Components ................................................................................351
9.3.1. Overview .................................................................................351
9.3.2. Internet Key Exchange (IKE) .......................................................351
9.3.3. IKE Authentication ....................................................................357
9.3.4. IPsec Protocols (ESP/AH) ...........................................................358
9.3.5. NAT Traversal ..........................................................................359
9.3.6. Algorithm Proposal Lists .............................................................360
9.3.7. Pre-shared Keys ........................................................................362
9.3.8. Identification Lists .....................................................................363
9.4. IPsec Tunnels ......................................................................................365
9.4.1. Overview .................................................................................365
9.4.2. LAN to LAN Tunnels with Pre-shared Keys ...................................366
9.4.3. Roaming Clients ........................................................................366
9.4.4. Fetching CRLs from an alternate LDAP server ................................371
9.4.5. Troubleshooting with ikesnoop .....................................................372
9.4.6. IPsec Advanced Settings .............................................................379
9.5. PPTP/L2TP .........................................................................................383
9.5.1. PPTP Servers ............................................................................383
9.5.2. L2TP Servers ............................................................................384
9.5.3. L2TP/PPTP Server advanced settings ............................................388
9.5.4. PPTP/L2TP Clients ....................................................................389
9.6. CA Server Access ................................................................................392
9.7. VPN Troubleshooting ...........................................................................395
9.7.1. General Troubleshooting .............................................................395
9.7.2. Troubleshooting Certificates ........................................................395
9.7.3. IPsec Troubleshooting Commands ................................................396
9.7.4. Management Interface Failure with VPN ........................................397
9.7.5. Specific Error Messages ..............................................................397
9.7.6. Specific Symptoms ....................................................................399
10. Traffic Management ......................................................................................402
10.1. Traffic Shaping ..................................................................................402
10.1.1. Overview ................................................................................402
10.1.2. Traffic Shaping in NetDefendOS .................................................403
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10.1.3. Simple Bandwidth Limiting .......................................................405
10.1.4. Limiting Bandwidth in Both Directions ........................................406
10.1.5. Creating Differentiated Limits with Chains ...................................407
10.1.6. Precedences ............................................................................408
10.1.7. Guarantees ..............................................................................410
10.1.8. Differentiated Guarantees ..........................................................410
10.1.9. Groups ...................................................................................411
10.1.10. Traffic Shaping Recommendations ............................................412
10.1.11. A Summary of Traffic Shaping .................................................414
10.1.12. More Pipe Examples ...............................................................414
10.2. IDP Traffic Shaping ............................................................................419
10.2.1. Overview ................................................................................419
10.2.2. Setup .....................................................................................419
10.2.3. Processing Flow .......................................................................420
10.2.4. The Importance of Specifying a Network ...................................... 420
10.2.5. A P2P Scenario ........................................................................421
10.2.6. Viewing Traffic Shaping Objects ................................................421
10.2.7. Guaranteeing Instead of Limiting Bandwidth .................................422
10.2.8. Logging .................................................................................423
10.3. Threshold Rules .................................................................................424
10.3.1. Overview ................................................................................424
10.3.2. Limiting the Connection Rate/Total Connections ...........................424
10.3.3. Grouping ................................................................................424
10.3.4. Rule Actions ...........................................................................425
10.3.5. Multiple Triggered Actions ........................................................425
10.3.6. Exempted Connections ..............................................................425
10.3.7. Threshold Rules and ZoneDefense ..............................................425
10.3.8. Threshold Rule Blacklisting .......................................................425
10.4. Server Load Balancing ........................................................................426
10.4.1. Overview ................................................................................426
10.4.2. Identifying the Servers ..............................................................427
10.4.3. The Load Distribution Mode ......................................................427
10.4.4. The Distribution Algorithm ........................................................428
10.4.5. Server Health Monitoring ..........................................................430
10.4.6. SLB_SAT Rules .......................................................................430
11. High Availability ..........................................................................................434
11.1. Overview ..........................................................................................434
11.2. HA Mechanisms .................................................................................436
11.3. HA Setup ..........................................................................................439
11.3.1. HA Hardware Setup .................................................................439
11.3.2. NetDefendOS Manual HA Setup .................................................440
11.3.3. Verifying the Cluster Functions ..................................................441
11.3.4. Unique Shared Mac Addresses ...................................................442
11.4. HA Issues .........................................................................................443
11.5. HA Advanced Settings ........................................................................444
12. ZoneDefense ................................................................................................446
12.1. Overview ..........................................................................................446
12.2. ZoneDefense Switches .........................................................................447
12.3. ZoneDefense Operation .......................................................................448
12.3.1. SNMP ....................................................................................448
12.3.2. Threshold Rules .......................................................................448
12.3.3. Manual Blocking and Exclude Lists .............................................448
12.3.4. ZoneDefense with Anti-Virus Scanning ........................................450
12.3.5. Limitations .............................................................................450
13. Advanced Settings .........................................................................................453
13.1. IP Level Settings ................................................................................453
13.2. TCP Level Settings .............................................................................457
13.3. ICMP Level Settings ...........................................................................462
13.4. State Settings .....................................................................................463
13.5. Connection Timeout Settings ................................................................465
13.6. Length Limit Settings ..........................................................................467
13.7. Fragmentation Settings ........................................................................469
13.8. Local Fragment Reassembly Settings .....................................................473
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13.9. Miscellaneous Settings ........................................................................474
A. Subscribing to Security Updates ........................................................................476
B. IDP Signature Groups .....................................................................................478
C. Verified MIME filetypes .................................................................................482
D. The OSI Framework .......................................................................................486
E. D-Link Worldwide Offices ...............................................................................487
Alphabetical Index .............................................................................................489
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List of Figures
1.1. Packet Flow Schematic Part I ...........................................................................21
1.2. Packet Flow Schematic Part II ..........................................................................22
1.3. Packet Flow Schematic Part III .........................................................................23
1.4. Expanded Apply Rules Logic ............................................................................24
3.1. VLAN Connections ........................................................................................92
3.2. Simplified NetDefendOS Traffic Flow .............................................................111
4.1. A Typical Routing Scenario ...........................................................................133
4.2. Using Local IP Address with an Unbound Network ............................................135
4.3. A Route Failover Scenario for ISP Access .........................................................140
4.4. The RLB Round Robin Algorithm ...................................................................152
4.5. The RLB Spillover Algorithm .........................................................................152
4.6. A Route Load Balancing Scenario ...................................................................155
4.7. Virtual Links Example 1 ................................................................................160
4.8. Virtual Links Example 2 ................................................................................161
4.9. Multicast Forwarding - No Address Translation .................................................166
4.10. Multicast Forwarding - Address Translation ....................................................168
4.11. Multicast Snoop .........................................................................................170
4.12. Multicast Proxy ..........................................................................................170
4.13. Non-transparent Mode Internet Access ...........................................................181
4.14. Transparent Mode Internet Access .................................................................182
4.15. Transparent Mode Scenario 1 ........................................................................183
4.16. Transparent Mode Scenario 2 ........................................................................185
4.17. An Example BPDU Relaying Scenario ...........................................................187
6.1. Deploying an ALG .......................................................................................207
6.2. HTTP ALG Processing Order .........................................................................210
6.3. SMTP ALG Processing Order .........................................................................220
6.4. DNSBL SPAM Filtering ................................................................................222
6.5. PPTP ALG Usage ........................................................................................228
6.6. TLS Termination ..........................................................................................252
6.7. Dynamic Content Filtering Flow .....................................................................259
6.8. IDP Database Updating .................................................................................279
7.1. NAT IP Address Translation ..........................................................................298
7.2. Anonymizing with NAT ................................................................................301
8.1. Normal LDAP Authentication ........................................................................325
8.2. LDAP for PPP with CHAP, MS-CHAPv1 or MS-CHAPv2 ..................................326
9.1. The AH protocol ..........................................................................................358
9.2. The ESP protocol .........................................................................................359
9.3. PPTP Client Usage .......................................................................................390
9.4. Certificate Validation Components ..................................................................393
10.1. Packet Flow of Pipe Rule Set to Pipe ..............................................................404
10.2. FwdFast Rules Bypass Traffic Shaping ...........................................................405
10.3. The Eight Pipe Precedences ..........................................................................408
10.4. Minimum and Maximum Pipe Precedence .......................................................409
10.5. Traffic grouped per IP address ......................................................................411
10.6. A Basic Traffic Shaping Scenario ..................................................................414
10.7. IDP Traffic Shaping P2P Scenario .................................................................421
10.8. A Server Load Balancing Configuration ..........................................................426
10.9. Connections from Three Clients ....................................................................428
10.10. Stickiness and Round-Robin .......................................................................429
10.11. Stickiness and Connection Rate ...................................................................429
D.1. The 7 Layers of the OSI Model ......................................................................486
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List of Examples
1. Example Notation .............................................................................................13
2.1. Enabling remote management via HTTPS ...........................................................31
2.2. Enabling SSH Remote Access ..........................................................................36
2.3. Listing Configuration Objects ...........................................................................48
2.4. Displaying a Configuration Object .....................................................................48
2.5. Editing a Configuration Object .........................................................................49
2.6. Adding a Configuration Object .........................................................................49
2.7. Deleting a Configuration Object ........................................................................50
2.8. Undeleting a Configuration Object ....................................................................50
2.9. Listing Modified Configuration Objects ..............................................................51
2.10. Activating and Committing a Configuration .......................................................51
2.11. Enable Logging to a Syslog Host .....................................................................55
2.12. Sending SNMP Traps to an SNMP Trap Receiver ...............................................56
2.13. RADIUS Accounting Server Setup ..................................................................62
2.14. Enabling SNMP Monitoring ...........................................................................66
2.15. Backing up the Entire System .........................................................................72
2.16. Complete Hardware Reset to Factory Defaults ...................................................72
3.1. Adding an IP Host ..........................................................................................76
3.2. Adding an IP Network .....................................................................................76
3.3. Adding an IP Range ........................................................................................76
3.4. Deleting an Address Object ..............................................................................77
3.5. Adding an Ethernet Address .............................................................................77
3.6. Listing the Available Services ...........................................................................80
3.7. Viewing a Specific Service ..............................................................................81
3.8. Adding a TCP/UDP Service .............................................................................82
3.9. Adding an IP Protocol Service ..........................................................................84
3.10. Enabling DHCP ...........................................................................................89
3.11. Defining a VLAN .........................................................................................94
3.12. Configuring a PPPoE client ............................................................................96
3.13. Creating an Interface Group ..........................................................................100
3.14. Displaying the ARP Cache ...........................................................................103
3.15. Flushing the ARP Cache ..............................................................................103
3.16. Defining a Static ARP Entry .........................................................................104
3.17. Adding an Allow IP Rule ..............................................................................114
3.18. Setting up a Time-Scheduled Policy ...............................................................115
3.19. Uploading a Certificate ................................................................................119
3.20. Associating Certificates with IPsec Tunnels .....................................................119
3.21. Setting the Current Date and Time .................................................................121
3.22. Setting the Time Zone .................................................................................122
3.23. Enabling DST ............................................................................................122
3.24. Enabling Time Synchronization using SNTP ....................................................123
3.25. Manually Triggering a Time Synchronization ..................................................124
3.26. Modifying the Maximum Adjustment Value ....................................................124
3.27. Forcing Time Synchronization ......................................................................125
3.28. Enabling the D-Link NTP Server ...................................................................125
3.29. Configuring DNS Servers .............................................................................128
4.1. Displaying the main Routing Table ..................................................................137
4.2. Displaying the Core Routes ............................................................................139
4.3. Creating a Policy-based Routing Table .............................................................148
4.4. Creating the Route ........................................................................................148
4.5. Policy-based Routing Configuration .................................................................149
4.6. Setting Up RLB ...........................................................................................155
4.7. Importing Routes from an OSPF AS into the Main Routing Table .........................163
4.8. Exporting the Default Route into an OSPF AS ...................................................163
4.9. Forwarding of Multicast Traffic using the SAT Multiplex Rule .............................167
4.10. Multicast Forwarding - Address Translation ....................................................169
4.11. IGMP - No Address Translation ....................................................................171
4.12. if1 Configuration ........................................................................................172
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4.13. if2 Configuration - Group Translation .............................................................173
4.14. Setting up Transparent Mode for Scenario 1 ....................................................184
4.15. Setting up Transparent Mode for Scenario 2 ....................................................185
5.1. Setting up a DHCP server ..............................................................................194
5.2. Checking DHCP Server Status ........................................................................194
5.3. Setting up Static DHCP .................................................................................196
5.4. Setting up a DHCP Relayer ............................................................................198
5.5. Creating an IP Pool .......................................................................................202
6.1. Setting up an Access Rule ..............................................................................206
6.2. Protecting an FTP Server with an ALG .............................................................213
6.3. Protecting FTP Clients ..................................................................................216
6.4. Protecting Phones Behind NetDefend Firewalls ..................................................241
6.5. H.323 with private IP addresses ......................................................................242
6.6. Two Phones Behind Different NetDefend Firewalls ............................................ 243
6.7. Using Private IP Addresses ............................................................................244
6.8. H.323 with Gatekeeper ..................................................................................245
6.9. H.323 with Gatekeeper and two NetDefend Firewalls ..........................................247
6.10. Using the H.323 ALG in a Corporate Environment ...........................................248
6.11. Configuring remote offices for H.323 .............................................................251
6.12. Allowing the H.323 Gateway to register with the Gatekeeper ..............................251
6.13. Stripping ActiveX and Java applets ................................................................256
6.14. Setting up a white and blacklist .....................................................................257
6.15. Enabling Dynamic Web Content Filtering .......................................................260
6.16. Enabling Audit Mode ..................................................................................262
6.17. Reclassifying a blocked site ..........................................................................263
6.18. Editing Content Filtering HTTP Banner Files ...................................................270
6.19. Activating Anti-Virus Scanning .....................................................................276
6.20. Configuring an SMTP Log Receiver ..............................................................286
6.21. Setting up IDP for a Mail Server ....................................................................286
6.22. Adding a Host to the Whitelist ......................................................................295
7.1. Adding a NAT Rule ......................................................................................300
7.2. Using NAT Pools .........................................................................................304
7.3. Enabling Traffic to a Protected Web Server in a DMZ ......................................... 306
7.4. Enabling Traffic to a Web Server on an Internal Network .................................... 308
7.5. Translating Traffic to Multiple Protected Web Servers ........................................310
8.1. Creating an Authentication User Group ............................................................331
8.2. User Authentication Setup for Web Access .......................................................331
8.3. Configuring a RADIUS Server .......................................................................332
8.4. Editing Content Filtering HTTP Banner Files ....................................................334
9.1. Using an Algorithm Proposal List ....................................................................361
9.2. Using a Pre-Shared key .................................................................................362
9.3. Using an Identity List ....................................................................................363
9.4. Setting up a PSK based VPN tunnel for roaming clients .......................................367
9.5. Setting up a Self-signed Certificate based VPN tunnel for roaming clients ...............368
9.6. Setting up CA Server Certificate based VPN tunnels for roaming clients .................369
9.7. Setting Up Config Mode ................................................................................371
9.8. Using Config Mode with IPsec Tunnels ............................................................371
9.9. Setting up an LDAP server .............................................................................371
9.10. Setting up a PPTP server ..............................................................................384
9.11. Setting up an L2TP server ............................................................................385
9.12. Setting up an L2TP Tunnel Over IPsec ...........................................................385
10.1. Applying a Simple Bandwidth Limit ..............................................................405
10.2. Limiting Bandwidth in Both Directions ...........................................................407
10.3. Setting up SLB ...........................................................................................431
12.1. A simple ZoneDefense scenario ....................................................................449
User Manual
12

Preface
Intended Audience
The target audience for this reference guide is Administrators who are responsible for configuring
and managing NetDefend Firewalls which are running the NetDefendOS operating system. This
guide assumes that the reader has some basic knowledge of networks and network security.
Text Structure and Conventions
The text is broken down into chapters and sub-sections. Numbered sub-sections are shown in the
table of contents at the beginning. An index is included at the end of the document to aid with
alphabetical lookup of subjects.
Where a "See chapter/section" link (such as: see Chapter 9, VPN) is provided in the main text, this
can be clicked to take the reader directly to that reference.
Text that may appear in the user interface of the product is designated by being in bold case. Where
a term is being introduced for the first time or being stressed it may appear in a italics.
Where console interaction is shown in the main text outside of an example, it will appear in a box
with a gray background.
Where a web address reference is shown in the text, clicking it will open the specified URL in a
browser in a new window (some systems may not allow this).
For example, http://www.dlink.com.
Screenshots
This guide contains a minimum of screenshots. This is deliberate and is done because the manual
deals specifically with NetDefendOS and administrators have a choice of management user
interfaces. It was decided that the manual would be less cluttered and easier to read if it concentrated
on describing how NetDefendOS functions rather than including large numbers of screenshots
showing how the various interfaces are used. Examples are given but these are largely textual
descriptions of management interface usage.
Examples
Examples in the text are denoted by the header Example and appear with a gray background as
shown below. They contain a CLI example and/or a Web Interface example as appropriate. (The
NetDefendOS CLI Reference Guide documents all CLI commands.)
Example 1. Example Notation
Information about what the example is trying to achieve is found here, sometimes with an explanatory image.
Command-Line Interface
The Command Line Interface example would appear here. It would start with the command prompt followed by
the command:
gw-world:/> somecommand someparameter=somevalue
Web Interface
The Web Interface actions for the example are shown here. They are also typically a numbered list showing what
13

items in the tree-view list at the left of the interface or in the menu bar or in a context menu need to be opened
followed by information about the data items that need to be entered:
1. Go to Item X > Item Y > Item Z
2. Now enter:
•DataItem1: datavalue1
•DataItem2: datavalue2
Highlighted Content
Special sections of text which the reader should pay special attention to are indicated by icons on the
left hand side of the page followed by a short paragraph in italicized text. Such sections are of the
following types with the following purposes:
Note
This indicates some piece of information that is an addition to the preceding text. It
may concern something that is being emphasized, or something that is not obvious or
explicitly stated in the preceding text.
Tip
This indicates a piece of non-critical information that is useful to know in certain
situations but is not essential reading.
Caution
This indicates where the reader should be careful with their actions as an undesirable
situation may result if care is not exercised.
Important
This is an essential point that the reader should read and understand.
Warning
This is essential reading for the user as they should be aware that a serious situation
may result if certain actions are taken or not taken.
Preface
14

Chapter 1. NetDefendOS Overview
This chapter outlines the key features of NetDefendOS.
• Features, page 15
• NetDefendOS Architecture, page 18
• NetDefendOS State Engine Packet Flow, page 21
1.1. Features
D-Link NetDefendOS is the base software engine that drives and controls the range of NetDefend
Firewall hardware products.
NetDefendOS as a Network Security Operating System
Designed as a network security operating system, NetDefendOS features high throughput
performance with high reliability plus super-granular control. In contrast to products built on top of
standard operating systems such as Unix or Microsoft Windows, NetDefendOS offers seamless
integration of all its subsystems, in-depth administrative control of all functionality, as well as a
minimal attack surface which helps to negate the risk from security attacks.
NetDefendOS Objects
From the administrator's perspective the conceptual approach of NetDefendOS is to visualize
operations through a set of logical building blocks or objects. These objects allow the configuration
of NetDefendOS in an almost limitless number of different ways. This granular control allows the
administrator to meet the requirements of the most demanding network security scenarios.
Key Features
NetDefendOS has an extensive feature set. The list below presents the key features of the product:
IP Routing NetDefendOS provides a variety of options for IP routing
including static routing, dynamic routing, as well as multicast
routing capabilities. In addition, NetDefendOS supports
features such as Virtual LANs, Route Monitoring, Proxy ARP
and Transparency. For more information, please see
Chapter 4, Routing.
Firewalling Policies NetDefendOS provides stateful inspection-based firewalling
for a wide range of protocols such as TCP, UDP and ICMP.
The administrator can define detailed firewalling policies
based on source/destination network/interface, protocol,
ports, user credentials, time-of-day and more. Section 3.5,
“The IP Rule Set”, describes how to set up these policies to
determine what traffic is allowed or rejected by
NetDefendOS.
Address Translation For functionality as well as security reasons, NetDefendOS
supports policy-based address translation. Dynamic Address
Translation (NAT) as well as Static Address Translation
(SAT) is supported, and resolves most types of address
translation needs. This feature is covered in Chapter 7,
Address Translation.
15

VPN NetDefendOS supports a range of Virtual Private Network
(VPN) solutions. NetDefendOS supports IPsec, L2TP and
PPTP based VPNs concurrently, can act as either server or
client for all of the VPN types, and can provide individual
security policies for each VPN tunnel. The details for this can
be found in Chapter 9, VPN which includes a summary of
setup steps in Section 9.2, “VPN Quick Start”.
TLS Termination NetDefendOS supports TLS termination so that the
NetDefend Firewall can act as the end point for connections
by HTTP web-browser clients (this feature is sometimes
called SSL termination). For detailed information, see
Section 6.2.10, “The TLS ALG”.
Anti-Virus Scanning NetDefendOS features integrated anti-virus functionality.
Traffic passing through the NetDefend Firewall can be
subjected to in-depth scanning for viruses, and virus sending
hosts can be black-listed and blocked. For details of this
feature, seeSection 6.4, “Anti-Virus Scanning”.
Note
Anti-Virus scanning is only available on certain
D-Link NetDefend product models.
Intrusion Detection and
Prevention To mitigate application-layer attacks towards vulnerabilities
in services and applications, NetDefendOS provides a
powerful Intrusion Detection and Prevention (IDP) engine.
The IDP engine is policy-based and is able to perform
high-performance scanning and detection of attacks and can
perform blocking and optional black-listing of attacking
hosts. More information about the IDP capabilities of
NetDefendOS can be found in Section 6.5, “Intrusion
Detection and Prevention”.
Note
Full IDP is available on all D-Link NetDefend
product models as a subscription service. On
some models, a simplified IDP subsystem is
provided as standard..
Web Content Filtering NetDefendOS provides various mechanisms for filtering web
content that is deemed inappropriate according to a web usage
policy. With Web Content Filtering (WCF) web content can
be blocked based on category (Dynamic WCF), malicious
objects can be removed from web pages and web sites can be
whitelisted or blacklisted. More information about this topic
can be found in Section 6.3, “Web Content Filtering”.
Note
Dynamic WCF is only available on some D-Link
NetDefend product models.
Traffic Management NetDefendOS provides broad traffic management capabilities
through Traffic Shaping,Threshold Rules (certain models
only) and Server Load Balancing.
Traffic Shaping enables limiting and balancing of bandwidth;
Threshold Rules allow specification of thresholds for sending
alarms and/or limiting network traffic; Server Load Balancing
1.1. Features Chapter 1. NetDefendOS Overview
16

enables a device running NetDefendOS to distribute network
load to multiple hosts. These features are discussed in detail
in Chapter 10, Traffic Management.
Note
Threshold Rules are only available on certain
D-Link NetDefend product models.
Operations and Maintenance Adminstrator management of NetDefendOS is possible
through either a Web-based User Interface (the WebUI) or via
a Command Line Interface (the CLI). NetDefendOS also
provides detailed event and logging capabilities plus support
for monitoring through SNMP. More detailed information
about this topic can be found in Chapter 2, Management and
Maintenance.
ZoneDefense NetDefendOS can be used to control D-Link switches using
the ZoneDefense feature. This allows NetDefendOS to isolate
portions of a network that contain hosts that are the source of
undesirable network traffic.
Note
NetDefendOS ZoneDefense is only available on
certain D-Link NetDefend product models.
NetDefendOS Documentation
Reading through the available documentation carefully will ensure that you get the most out of your
NetDefendOS product. In addition to this document, the reader should also be aware of the
companion reference guides:
• The CLI Reference Guide which details all NetDefendOS CLI commands.
• The NetDefendOS Log Reference Guide which details all NetDefendOS log event messages.
Together, these documents form the essential reference material for NetDefendOS operation.
1.1. Features Chapter 1. NetDefendOS Overview
17

1.2. NetDefendOS Architecture
1.2.1. State-based Architecture
The NetDefendOS architecture is centered around the concept of state-based connections.
Traditional IP routers or switches commonly inspect all packets and then perform forwarding
decisions based on information found in the packet headers. With this approach, packets are
forwarded without any sense of context which eliminates any possibility to detect and analyze
complex protocols and enforce corresponding security policies.
Stateful Inspection
NetDefendOS employs a technique called stateful inspection which means that it inspects and
forwards traffic on a per-connection basis. NetDefendOS detects when a new connection is being
established, and keeps a small piece of information or state in its state table for the lifetime of that
connection. By doing this, NetDefendOS is able to understand the context of the network traffic
which enables it to perform in-depth traffic scanning, apply bandwidth management and a variety of
other functions.
The stateful inspection approach additionally provides high throughput performance with the added
advantage of a design that is highly scalable. The NetDefendOS subsystem that implements stateful
inspection will sometimes be referred to in documentation as the NetDefendOS state-engine.
1.2.2. NetDefendOS Building Blocks
The basic building blocks in NetDefendOS are interfaces, logical objects and various types of rules
(or rule sets).
Interfaces
Interfaces are the doorways through which network traffic enters or leaves the NetDefend Firewall.
Without interfaces, a NetDefendOS system has no means for receiving or sending traffic.
The following types of interface are supported in NetDefendOS:
•Physical interfaces - These correspond to the actual physical Ethernet ports.
•Sub-interfaces - These include VLAN and PPPoE interfaces.
•Tunnel interfaces - Used for receiving and sending traffic through VPN tunnels.
Interface Symmetry
The NetDefendOS interface design is symmetric, meaning that the interfaces of the device are not
fixed as being on the "insecure outside" or "secure inside" of a network topology. The notion of
what is inside and outside is totally for the administrator to define.
Logical Objects
Logical objects can be seen as predefined building blocks for use by the rule sets. The address book,
for instance, contains named objects representing host and network addresses.
Another example of logical objects are services which represent specific protocol and port
combinations. Also important are the Application Layer Gateway (ALG) objects which are used to
define additional parameters on specific protocols such as HTTP, FTP, SMTP and H.323.
1.2. NetDefendOS Architecture Chapter 1. NetDefendOS Overview
18

NetDefendOS Rule Sets
Finally, rules which are defined by the administrator in the various rule sets are used for actually
implementing NetDefendOS security policies. The most fundamental set of rules are the IP Rules,
which are used to define the layer 3 IP filtering policy as well as carrying out address translation and
server load balancing. The Traffic Shaping Rules define the policy for bandwidth management, the
IDP Rules control the behavior of the intrusion prevention engine and so on.
1.2.3. Basic Packet Flow
This section outlines the basic flow in the state-engine for packets received and forwarded by
NetDefendOS. The following description is simplified and might not be fully applicable in all
scenarios, however, the basic principles will be valid for all NetDefendOS deployments.
1. An Ethernet frame is received on one of the Ethernet interfaces in the system. Basic Ethernet
frame validation is performed and the packet is dropped if the frame is invalid.
2. The packet is associated with a Source Interface. The source interface is determined as follows:
• If the Ethernet frame contains a VLAN ID (Virtual LAN identifier), the system checks for a
configured VLAN interface with a corresponding VLAN ID. If one is found, that VLAN
interface becomes the source interface for the packet. If no matching interface is found, the
packet is dropped and the event is logged.
• If the Ethernet frame contains a PPP payload, the system checks for a matching PPPoE
interface. If one is found, that interface becomes the source interface for the packet. If no
matching interface is found, the packet is dropped and the event is logged.
• If none the above is true, the receiving Ethernet interface becomes the source interface for
the packet.
3. The IP datagram within the packet is passed on to the NetDefendOS Consistency Checker. The
consistency checker performs a number of sanity checks on the packet, including validation of
checksums, protocol flags, packet length and so on. If the consistency checks fail, the packet
gets dropped and the event is logged.
4. NetDefendOS now tries to lookup an existing connection by matching parameters from the
incoming packet. A number of parameters are used in the match attempt, including the source
interface, source and destination IP addresses and IP protocol.
If a match cannot be found, a connection establishment process starts which includes steps
from here to 9below. If a match is found, the forwarding process continues at step 10 below.
5. The Access Rules are evaluated to find out if the source IP address of the new connection is
allowed on the received interface. If no Access Rule matches then a reverse route lookup will
be done. In other words, by default, an interface will only accept source IP addresses that
belong to networks routed over that interface. If the Access Rules or the reverse route lookup
determine that the source IP is invalid, then the packet is dropped and the event is logged.
6. A route lookup is being made using the appropriate routing table. The destination interface for
the connection has now been determined.
7. The IP rules are now searched for a rule that matches the packet. The following parameters are
part of the matching process:
• Source and destination interfaces
• Source and destination network
• IP protocol (for example TCP, UDP, ICMP)
1.2.3. Basic Packet Flow Chapter 1. NetDefendOS Overview
19

• TCP/UDP ports
• ICMP types
• Point in time in reference to a predefined schedule
If a match cannot be found, the packet is dropped.
If a rule is found that matches the new connection, the Action parameter of the rule decides
what NetDefendOS should do with the connection. If the action is Drop, the packet is dropped
and the event is logged according to the log settings for the rule.
If the action is Allow, the packet is allowed through the system. A corresponding state will be
added to the connection table for matching subsequent packets belonging to the same
connection. In addition, the service object which matched the IP protocol and ports might have
contained a reference to an Application Layer Gateway (ALG) object. This information is
recorded in the state so that NetDefendOS will know that application layer processing will have
to be performed on the connection.
Finally, the opening of the new connection will be logged according to the log settings of the
rule.
Note: Additional actions
There are actually a number of additional actions available such as address
translation and server load balancing. The basic concept of dropping and
allowing traffic is still the same.
8. The Intrusion Detection and Prevention (IDP) Rules are now evaluated in a similar way to the
IP rules. If a match is found, the IDP data is recorded with the state. By doing this,
NetDefendOS will know that IDP scanning is supposed to be conducted on all packets
belonging to this connection.
9. The Traffic Shaping and the Threshold Limit rule sets are now searched. If a match is found,
the corresponding information is recorded with the state. This will enable proper traffic
management on the connection.
10. From the information in the state, NetDefendOS now knows what to do with the incoming
packet:
• If ALG information is present or if IDP scanning is to be performed, the payload of the
packet is taken care of by the TCP Pseudo-Reassembly subsystem, which in turn makes use
of the different Application Layer Gateways, layer 7 scanning engines and so on, to further
analyze or transform the traffic.
• If the contents of the packet is encapsulated (such as with IPsec, PPTP/L2TP or some other
type of tunneled protocol), then the interface lists are checked for a matching interface. If
one is found, the packet is decapsulated and the payload (the plaintext) is sent into
NetDefendOS again, now with source interface being the matched tunnel interface. In other
words, the process continues at step 3 above.
• If traffic management information is present, the packet might get queued or otherwise be
subjected to actions related to traffic management.
11. Eventually, the packet will be forwarded out on the destination interface according to the state.
If the destination interface is a tunnel interface or a physical sub-interface, additional
processing such as encryption or encapsulation might occur.
The next section provides a set of diagrams illustrating the flow of packets through NetDefendOS.
1.2.3. Basic Packet Flow Chapter 1. NetDefendOS Overview
20