Cisco WS-C2950SX-48-SI User manual

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Catalyst 4500 Series, Catalyst 2948G,
Catalyst 2980G Switches Software
Configuration Guide
Software Release 8.1
Customer Order Number: DOC-7815486=
Text Part Number: 78-15486-01

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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
Copyright © 2000-2003, Cisco Systems, Inc. All rights reserved.

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CONTENTS
Preface xxiii
Audience xxiii
Organization xxiii
Related Documentation xxv
Conventions xxvi
Obtaining Documentation xxvii
Cisco.com xxvii
Documentation CD-ROM xxvii
Ordering Documentation xxvii
Documentation Feedback xxviii
Obtaining Technical Assistance xxviii
Cisco.com xxviii
Technical Assistance Center xxix
Obtaining AdditionalPublications and Information xxx
CHAPTER 1Product Overview 1-1
Catalyst 4000 Series Switches 1-1
Catalyst 2948G Switch 1-2
Catalyst 2980G Switch 1-3
Supervisor Engine Software 1-3
CHAPTER 2Using the Command-Line Interface 2-1
Switch CLI Overview 2-1
Accessing the Switch CLI 2-2
Accessing the CLI Through the Console Port 2-2
Accessing the CLI Through Telnet 2-3
Switch CLI Command Modes 2-3
Accessing Help 2-4
Command-Line Editing 2-5
History Substitution 2-6
Abbreviating a Command 2-6
Completing a Partial Command 2-6
Scrolling Through Command Output 2-6

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Using Command Aliases 2-7
Specifying Modules, Ports, and VLANs 2-7
Specifying MAC Addresses 2-8
Specifying IP Addresses, Host Names, and IP Aliases 2-8
ROM Monitor CLI 2-9
Example of a Catalyst 4003 Bootup Display 2-9
CHAPTER 3Configuring the Switch IP Address and Default Gateway 3-1
Understanding How the Switch Management Interfaces Work 3-1
Understanding How Automatic IP Configuration Works 3-2
Automatic IP Configuration Overview 3-2
Understanding DHCP 3-3
Understanding RARP 3-4
Preparing to Configure the IP Address and Default Gateway 3-4
Default IP Address and Default Gateway Configuration 3-5
Setting the In-Band (sc0) Interface IP Address 3-5
Setting the Management Ethernet (me1) Interface IP Address 3-6
Configuring Default Gateways 3-6
Configuring the SLIP (sl0) Interface on the Console Port 3-8
Using DHCP or RARP to Obtain an IP Address Configuration 3-9
Renewing and Releasing a DHCP-Assigned IP Address 3-10
CHAPTER 4Configuring Ethernet and Fast EthernetSwitching 4-1
Understanding How Ethernet Works 4-1
Ethernet Overview 4-1
Switching Frames Between Segments 4-2
Building the Address Table 4-2
Default Ethernet and Fast Ethernet Configurations 4-2
Configuring Ethernetand Fast Ethernet Ports 4-3
Setting Ethernet and Fast Ethernet Port Names 4-3
Setting Ethernet and Fast Ethernet PortPriority Levels 4-4
Setting Ethernet and Fast Ethernet PortSpeeds 4-4
Setting Ethernet and Fast Ethernet Port Duplex Modes 4-5
Setting Ethernet and Fast Ethernet Port Debounce Timers 4-6
Configuring errdisable State Ethernetand Fast Ethernet Port Timeout Periods 4-7
Checking Ethernet and Fast Ethernet PortConnectivity 4-8

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CHAPTER 5Configuring Gigabit Ethernet Switching 5-1
Understanding How Gigabit Ethernet Works 5-1
Understanding How Gigabit Ethernet Flow Control Works 5-1
Understanding How Port Negotiation Works 5-3
Understanding How Oversubscribed Gigabit Ethernet Works 5-3
Default Gigabit Ethernet Configuration 5-6
Configuring Gigabit Ethernet Ports 5-7
Assigning Gigabit Ethernet PortNames 5-7
Configuring Gigabit Ethernet Port Priority Levels 5-7
Configuring Flow Control on Gigabit Ethernet Ports 5-8
Enabling Port Negotiation on Gigabit Ethernet Ports 5-9
Disabling Port Negotiation 5-9
Configuring errdisable State Gigabit Ethernet Port Timeout Periods 5-9
Checking GigabitEthernet Port Connectivity 5-10
CHAPTER 6Configuring Fast EtherChannel and Gigabit EtherChannel 6-1
Understanding How EtherChannel Works 6-1
EtherChannelOverview 6-2
Understanding Frame Distribution 6-2
Hardware Support for EtherChannel 6-2
PAgP and LACP 6-2
EtherChannelConfiguration Guidelines and Restrictions 6-3
Guidelines for Configuring a Port 6-3
Guidelines for Configuring VLANs and Trunks 6-4
EtherChannelInteraction with other Features 6-4
Understanding the PAgP 6-5
PAgP Modes 6-5
Understanding Administrative Groups and EtherChannel IDs 6-6
Configuring EtherChannel Using PAgP 6-6
Creating an EtherChannel 6-7
Defining an EtherChannel Administrative Group 6-7
Setting the EtherChannel Spanning Tree PortCost 6-8
Setting the EtherChannel Spanning Tree PortVLAN Cost 6-9
Removing an EtherChannel Bundle 6-9
Displaying EtherChannel Configuration Information 6-10
Displaying EtherChannel Traffic Statistics 6-11
Displaying EtherChannel PAgP Statistics 6-12
EtherChannelConfiguration Examples 6-12

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Configuration Example of a Four-Port Fast EtherChannel 6-12
Configuration Example of Two-Port Gigabit EtherChannel 6-14
Understanding the LACP 6-16
LACP Modes 6-16
LACP Parameters 6-17
Configuring EtherChannel Using LACP 6-18
Specifying the EtherChannel Protocol 6-18
Specifying the System Priority 6-19
Specifying the Port Priority 6-19
Specifying an Administrative Key Value 6-19
Changing the Channel Mode 6-20
Specifying the Channel Path Cost 6-21
Specifying the Channel VLAN Cost 6-21
Clearing LACP Statistics 6-21
Displaying EtherChannel Traffic Utilization 6-21
Disabling an EtherChannel 6-22
Displaying Spanning Tree-Related Information for EtherChannels 6-22
CHAPTER 7Configuring Spanning Tree 7-1
Understanding How STPs Work 7-2
Understanding How a Topology Is Created 7-2
Understanding Howa Switch or Port Becomes the Root Switch or Root Port 7-3
Understanding BPDUs 7-4
Calculating and Assigning Port Costs 7-4
Understanding Spanning Tree Port States 7-5
Understanding How PVST+ and MISTP Modes Work 7-11
PVST+ Mode 7-12
Rapid PVST+ 7-12
MISTP Mode 7-12
MISTP-PVST+ Mode 7-13
Understanding How Bridge Identifiers Work 7-13
MAC Address Allocation 7-13
MAC Address Reduction 7-13
Understanding How MST Works 7-14
Rapid Spanning Tree Protocol 7-16
MST-to-SST Interoperability 7-17
Common Spanning Tree 7-18
MST Instances 7-18
MST Configuration 7-18

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MST Region 7-19
Message Age and Hop Count 7-21
MST-to-PVST+ Interoperability 7-21
Understanding How BPDU Skewing Works 7-22
Using PVST+ 7-22
Default PVST+ Configuration 7-23
Setting the PVST+ Bridge ID Priority 7-23
Configuring the PVST+ Port Cost 7-25
Configuring PVST+ Port Priority 7-25
Configuring the PVST+ Default Port Cost Mode 7-26
Configuring the PVST+ Port VLAN Cost 7-26
Configuring the PVST+ Port VLAN Priority 7-27
Disabling the PVST+ Mode on a VLAN 7-28
Using Rapid PVST+ 7-28
Using MISTP-PVST+ or MISTP 7-30
Default MISTP Mode Configuration 7-30
Setting the MISTP-PVST+ Mode or MISTP Mode 7-31
Configuring the MISTP Bridge ID Priority 7-32
Enabling an MISTP Instance 7-36
Mapping VLANs to an MISTP Instance 7-36
Disabling MISTP-PVST+ or MISTP 7-39
Configuring a Root Switch 7-39
Configuring a Primary Root Switch 7-39
Configuring a Secondary Root Switch 7-40
Configuring a Root Switch to Improve Convergence 7-41
Using Root Guard—Preventing Switches from Becoming Root 7-43
Displaying Spanning Tree BPDU Statistics 7-43
Configuring Spanning Tree Timers 7-44
Configuring the Hello Time 7-44
Configuring the Forward Delay Time 7-45
Configuring the Maximum Aging Time 7-45
Configuring MST 7-46
Enabling MST 7-46
Mapping and Unmapping VLANs to an MST Instance 7-54
Configuring Spanning Tree BPDU Skewing 7-57
CHAPTER 8Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast,and
Loop Guard 8-1
Understanding How PortFast Works 8-1

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Understanding How PortFast BPDU Guard Works 8-2
Understanding How PortFast BPDU Filtering Works 8-2
Understanding How UplinkFast Works 8-3
Understanding How BackboneFast Works 8-4
Understanding How Loop Guard Works 8-6
Configuring PortFast 8-8
Enabling PortFast on an Access Port 8-8
Enabling PortFast on a Trunk Port 8-9
Disabling PortFast 8-10
Resetting PortFast 8-11
Configuring PortFast BPDU Guard 8-11
Enabling PortFast BPDU Guard 8-11
Disabling PortFast BPDU Guard 8-12
Configuring PortFast BPDU Filtering 8-13
Enabling PortFast BPDU Filtering 8-13
Disabling PortFast BPDU Filtering 8-14
Configuring UplinkFast 8-15
Enabling UplinkFast 8-15
Disabling UplinkFast 8-16
Configuring BackboneFast 8-17
Enabling BackboneFast 8-17
Displaying BackboneFast Statistics 8-17
Disabling BackboneFast 8-18
Configuring Loop Guard 8-18
Enabling Loop Guard 8-18
Disabling Loop Guard 8-19
CHAPTER 9Configuring VTP 9-1
Understanding How VTP Version 1 and Version 2 Work 9-1
Understanding the VTP Domain 9-2
Understanding VTPModes 9-2
Understanding VTPAdvertisements 9-3
Understanding VTPVersion 2 9-3
Understanding VTPPruning 9-4
Default VTP Version 1 and Version 2 Configuration 9-5
VTP Version 1 and Version 2 Configuration Guidelines 9-6
Configuring VTP Version 1 andVersion 2 9-6
Configuring a VTP Server 9-7

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Configuring a VTP Client 9-7
Configuring VTP (VTP Transparent Mode) 9-8
Disabling VTP Using the Off Mode 9-9
Enabling VTP Version 2 9-9
Disabling VTP Version 2 9-10
Enabling VTP Pruning 9-11
Disabling VTP Pruning 9-12
Displaying VTP Statistics 9-12
Understanding How VTP Version 3 Works 9-13
VTP Version 3 Authentication 9-13
VTP Version 3 Per-Port Configuration 9-14
VTP Version 3 Domains,Modes, and Partitions 9-14
VTP Version 3 Modes 9-18
VTP Version 3 Databases 9-19
Default VTP Version 3 Configuration 9-22
Configuring VTP Version 3 9-22
Enabling VTP Version 3 9-22
Changing VTP Version 3 Modes 9-23
Configuring VTP Version 3 Passwords 9-27
Configuring a VTP Version 3 Takeover 9-28
Disabling VTP Version 3 on a Per-PortBasis 9-29
VTP Version 3 show Commands 9-29
CHAPTER 10 Configuring VLANs 10-1
Understanding How VLANs Work 10-1
VLAN Ranges 10-3
Configurable VLAN Parameters 10-4
VLAN Default Configuration 10-4
VLAN Configuration Guidelines 10-5
Configuring VLANs on the Switch 10-6
Creating or Modifying an Ethernet VLAN 10-6
Creating or Modifying a Normal-Range Ethernet VLAN 10-7
Creating or Modifying an Extended-Range VLAN 10-9
Assigning Switch Ports to a VLAN 10-10
Mapping 802.1Q VLANs to ISL VLANs 10-11
Clearing 802.1Q-to-ISL VLAN Mappings 10-12
Deleting a VLAN 10-12
Configuring Auxiliary VLANs 10-13
Understanding Auxiliary VLANs 10-13

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Configuring PrivateVLANs 10-16
Private VLAN Configuration Guidelines 10-17
Creating a Private VLAN 10-19
Viewing the Port Capability of a Private VLAN Port 10-22
Deleting a Private VLAN 10-22
Deleting an Isolated orCommunity VLAN 10-23
Deleting a Private VLAN Mapping 10-23
CHAPTER 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports 11-1
Understanding How VLAN Trunks Work 11-1
Trunking Overview 11-1
Trunking Modes and Encapsulation Types 11-2
Trunking Support 11-3
802.1Q Trunk Restrictions 11-4
Default Trunk Configuration 11-5
Configuring a Trunk Link 11-5
Configuring an 802.1Q Trunk 11-5
Defining the Allowed VLANs on a Trunk 11-6
Disabling a Trunk Port 11-7
Disabling VLAN 1 on a Trunk Link 11-8
Example VLAN Trunk Configurations 11-9
802.1Q Trunk over a Gigabit EtherChannel Link Example 11-9
Load-Sharing VLAN Traffic over Parallel Trunks Example 11-13
802.1Q Nonegotiate Trunk Configuration Example 11-19
CHAPTER 12 Configuring Dynamic VLAN Membership with VMPS 12-1
Understanding How VMPS Works 12-1
VMPS and Dynamic Port Hardware and Software Requirements 12-2
Default VMPS and Dynamic Port Configuration 12-3
Configuration Guidelines for Dynamic Ports and VMPS 12-3
Configuring VMPS 12-4
Creating the VMPS Database 12-4
Configuring the VMPS Server 12-7
Configuring VMPS Clients 12-8
Monitoring VMPS 12-9
Maintaining VMPS 12-9
Configuring Static Ports 12-10
Troubleshooting VMPS and Dynamic Port VLAN Membership 12-11