Draytek VigorSwitch G1240 User manual

i

VigorSwitch G1240 User’s Guide
ii
VigorSwitch G1240
24 Gigabit Port Web Smart Switch
User’s Guide
Version: 1.0
Firmware Version: V1.47
Date: 05/09/2011

VigorSwitch G1240 User’s Guide iii
Copyright Information
Copyright
Declarations
Copyright 2011 All rights reserved. This publication contains information that is
protected by copyright. No part may be reproduced, transmitted, transcribed,
stored in a retrieval system, or translated into any language without written
permission from the copyright holders.
Trademarks
The following trademarks are used in this document:
zMicrosoft is a registered trademark of Microsoft Corp.
zWindows, Windows 95, 98, Me, NT, 2000, XP and Explorer are
trademarks of Microsoft Corp.
zApple and Mac OS are registered trademarks of Apple Inc.
zOther products may be trademarks or registered trademarks of their
respective manufacturers.
Caution and Electronic Emission Notices
Caution
Circuit devices are sensitive to static electricity, which can damage their delicate
electronics. Dry weather conditions or walking across a carpeted floor may cause you
to acquire a static electrical charge.
To protect your device, always:
zTouch the metal chassis of your computer to ground the static electrical charge
before you pick up the circuit device.
zPick up the device by holding it on the left and right edges only.
Warranty
We warrant to the original end user (purchaser) that the device will be free from any
defects in workmanship or materials for a period of one (1) years from the date of
purchase from the dealer. Please keep your purchase receipt in a safe place as it
serves as proof of date of purchase. During the warranty period, and upon proof of
purchase, should the product have indications of failure due to faulty workmanship
and/or materials, we will, at our discretion, repair or replace the defective products or
components, without charge for either parts or labor, to whatever extent we deem
necessary tore-store the product to proper operating condition. Any replacement will
consist of a new or re-manufactured functionally equivalent product of equal value,
and will be offered solely at our discretion. This warranty will not apply if the
product is modified, misused, tampered with, damaged by an act of God, or subjected
to abnormal working conditions. The warranty does not cover the bundled or licensed
software of other vendors. Defects which do not significantly affect the usability of
the product will not be covered by the warranty. We reserve the right to revise the
manual and online documentation and to make changes from time to time in the
contents hereof without obligation to notify any person of such revision or changes.
Be a Registered
Owner Web registration is preferred. You can register your Vigor device via
http://www.draytek.com.
Firmware & Tools
Updates Due to the continuous evolution of DrayTek technology, all devices will be regularly
upgraded. Please consult the DrayTek web site for more information on newest
firmware, tools and documents.
http://www.draytek.com

VigorSwitch G1240 User’s Guide
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European Community Declarations
Manufacturer: DrayTek Corp.
Address: No. 26, Fu Shing Road, HuKou township, HsinChu Industrial Park, Hsin-Chu, Taiwan 303
Product: VigorSwitch Series Device
The product conforms to the requirements of Electro-Magnetic Compatibility (EMC) Directive 2004/108/EC by
complying with the requirements set forth in EN55022/Class A and EN55024/Class A.
The product conforms to the requirements of Low Voltage (LVD) Directive 2006/95/EC by complying with the
requirements set forth in EN6095-1.
Federal Communications Commission (FCC) Statement
This equipment has been tested and found to comply with the limits for a class A computing device pursuant to
Subpart J of part 15 of FCC Rules, which are designed to provide reasonable protection against such interference
when operated in a commercial environment.

VigorSwitch G1240 User’s Guide v
T
Ta ab bl le e o of f C Co on nt te en nt ts s
Introduction ....................................................................................................1
1.1 Overview................................................................................................................................. 1
1.2 Features.................................................................................................................................. 2
1.3 Packing List............................................................................................................................. 3
1.4 LED Indicators and Connectors.............................................................................................. 4
1.5 Hardware Installation .............................................................................................................. 5
1.5.1 Connecting the SFP Fiber Transceiver to the Chassis .................................................... 5
1.5.2 Installing Optional SFP Fiber Transceivers to the switch................................................. 6
1.5.3 Installing Chassis to a 19-Inch Wiring Closet Rail............................................................ 6
1.5.4 Cabling Requirements......................................................................................................6
1.5.5 Configuring the Management Agent of Switch............................................................... 11
1.5.6 IP Address Assignment .................................................................................................. 12
1.6 Typical Applications............................................................................................................... 16
Basic Concept and Management ................................................................18
2.1 What’s the Ethernet............................................................................................................... 18
2.2 Media Access Control (MAC)................................................................................................ 20
2.3 Flow Control.......................................................................................................................... 25
2.4 How does a switch work?...................................................................................................... 27
Terminology............................................................................................................................. 27
2.5 Virtual LAN............................................................................................................................ 30
2.6 Link Aggregation ................................................................................................................... 35
Operation of Web-based Management.......................................................39
3.1 Web Management Home Overview...................................................................................... 40
3.1.1 The Information of Page Layout..................................................................................... 40
3.2 System .................................................................................................................................. 41
3.2.1 System Information and IP Configuration....................................................................... 41
3.3 Port........................................................................................................................................ 43
3.3.1 Port Configuration........................................................................................................... 43
3.3.2 Detailed Port Statistics.................................................................................................... 44
3.4 VLAN Mode........................................................................................................................... 47
3.4.1 Tag-Based Group...........................................................................................................48
3.4.2 Port-based Group........................................................................................................... 51

VigorSwitch G1240 User’s Guide
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3.5 Filter ...................................................................................................................................... 52
3.6 QoS....................................................................................................................................... 53
3.6.1 QoS Configuration.......................................................................................................... 53
3.6.2 Rate Limit........................................................................................................................ 55
3.6.3 Storm Control.................................................................................................................. 56
3.6.4 SNMP.............................................................................................................................. 57
3.6.5 802.1X............................................................................................................................. 59
3.7 Trunk ..................................................................................................................................... 64
3.7.1 Aggregation .................................................................................................................... 64
3.7.2 LACP............................................................................................................................... 65
3.8 RSTP..................................................................................................................................... 66
3.9 Mirroring................................................................................................................................ 68
3.10 IGMP Snooping................................................................................................................... 68
3.11 Monitoring............................................................................................................................ 69
3.11.1 LACP Status ................................................................................................................. 69
3.11.2 RSTP Status................................................................................................................. 70
3.11.3 IGMP Status ................................................................................................................. 71
3.12 Configuration File................................................................................................................ 73
3.13 Diagnostics.......................................................................................................................... 73
3.13.1 Ping............................................................................................................................... 73
3.14 Maintenance........................................................................................................................ 74
3.14.1 Warm Restart................................................................................................................ 74
3.14.2 Firmware Upgrade........................................................................................................ 75
3.14.3 Factory Defaults............................................................................................................ 75
3.15 Logout................................................................................................................................. 76
Trouble Shooting..........................................................................................77
4.1 Resolving No Link Condition.................................................................................................77
4.2 Q & A..................................................................................................................................... 77

VigorSwitch G1240 User’s Guide 1
I In nt tr ro od du uc ct ti io on n
1
1. .1 1 O Ov ve er rv vi ie ew w
The 24-port Gigabit Web Smart Switch is a standard switch that meets all IEEE 802.3/u/x/z
Gigabit, Fast Ethernet specifications. The switch has 20 10/100/1000Mbps TP ports and 4
Gigabit TP/SFP transceiver slots. It supports console, telnet, http and SNMP interface for
switch management. The network administrator can logon the switch to monitor, configure
and control each port’s activity. In addition, the switch implements the QoS (Quality of
Service), VLAN, and Trunking. It is suitable for office application.
In this switch, Port 21, 22, 23, 24 includes two types of media --- TP and SFP Fiber (LC,
BiDi-SC…); this port supports 10/100/1000Mbps TP or 1000Mbps SFP Fiber with
auto-detected function. 1000Mbps SFP Fiber transceiver is used for high-speed connection
expansion.
¾1000Mbps LC, Multi-Mode, SFP Fiber transceiver
¾1000Mbps LC, 10km, SFP Fiber transceiver
¾1000Mbps LC, 30km, SFP Fiber transceiver
¾1000Mbps LC, 50km, SFP Fiber transceiver
¾1000Mbps BiDi LC, 20km, 1550nm SFP Fiber WDM transceiver
¾1000Mbps BiDi LC, 20km, 1310nm SFP Fiber WDM transceiver
10/100/1000Mbps TP is a standard Ethernet port that meets all IEEE 802.3/u/x/z Gigabit,
Fast Ethernet specifications. 1000Mbps SFP Fiber transceiver is a Gigabit Ethernet port
that fully complies with all IEEE 802.3z and 1000Base-SX/LX standards.
1000Mbps Single Fiber WDM (BiDi) transceiver is designed with an optic Wavelength
Division Multiplexing (WDM) technology that transports bi-directional full duplex signal
over a single fiber simultaneously.

VigorSwitch G1240 User’s Guide
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Below shows key features of this device:
Q
Qo oS S
The switch offers powerful QoS function. This function supports 802.1p VLAN tag priority
and DSCP on Layer 3 of network framework.
V
VL LA AN N
Support Port-based VLAN and IEEE802.1Q Tag VLAN. Support 24 active VLANs and
VLAN ID 1~4094.
P
Po or rt t T Tr ru un nk ki in ng g
Allows one or more links to be aggregated together to form a Link Aggregation Group by
the static setting.
1
1. .2 2 F Fe ea at tu ur re es s
The VigorSwitch G1240, a standalone off-the-shelf switch, provides the comprehensive
features listed below for users to perform system network administration and efficiently
and securely serve your network.
H
Ha ar rd dw wa ar re e
z20 10/100/1000Mbps Auto-negotiation Gigabit Ethernet TP ports
z4 10/100/1000Mbps TP or 1000Mbps SFP Fiber dual media auto sense
z1392KB on-chip frame buffer
zJumbo frame support
zProgrammable classifier for QoS (Layer 2/Layer 3)
z8K MAC address and support VLAN ID(1~4094)
zPer-port shaping, policing, and Broadcast Storm Control
zIEEE802.1Q Q-in-Q nested VLAN support
zFull-duplex flow control (IEEE802.3x) and half-duplex backpressure
zExtensive front-panel diagnostic LEDs; System: Power, TP Port1-24: LINK/ACT,
10/100/1000Mbps, SFP Port 21-24: SFP(LINK/ACT)
M
Ma an na ag ge em me en nt t
zSupports concisely the status of port and easily port configuration
zSupports per port traffic monitoring counters
zSupports a snapshot of the system Information when you login
zSupports port mirror function
zSupports the static trunk function
zSupports 802.1Q VLAN
zSupports user management and limits three users to login
zMaximal packet length can be up to 9600 bytes for jumbo frame application
zSupports Broadcasting Suppression to avoid network suspended or crashed
zSupports to send the trap event while monitored events happened

VigorSwitch G1240 User’s Guide 3
zSupports default configuration which can be restored to overwrite the current
configuration which is working on via web browser and CLI
zSupports on-line plug/unplug SFP modules
zSupports Quality of Service (QoS) for real time applications based on the
information taken from Layer 2 to Layer 4, such as VoIP
zBuilt-in web-based management and CLI management, providing a more
convenient UI for the user
1
1. .3 3 P Pa ac ck ki in ng g L Li is st t
Before you start installing the switch, verify that the package contains the following:
zVigorSwitch G1240
zAC Power Cord
zCD
zRubber feet
zRack mount kit
Please notify your sales representative immediately if any of the aforementioned items is
missing or damaged.
O
Op pt ti io on na al l M Mo od du ul le es s
In the switch, Port 21~24 include two types of media --- TP and SFP Fiber (LC,
BiDi-SC…); they support 10/100/1000Mbps TP or 1000Mbps SFP Fiber with
auto-detected function. 1000Mbps SFP Fiber transceiver is used for high-speed connection
expansion; nine optional SFP types provided for the switch are listed below:
z1000Mbps LC, MM, SFP Fiber transceiver (SFP.0LC.202)
z1000Mbps LC, SM 10km, SFP Fiber transceiver (SFP.0LC.212.10)
z1000Mbps LC, SM 30km, SFP Fiber transceiver (SFP.0LC.212.30)
z1000Mbps LC, SM 50km, SFP Fiber transceiver (SFP.0LC.212.50)
z1000Mbps LC, SM 70km, SFP Fiber transceiver (SFP.0LC.212.70)
z1000Mbps LC, SM 110km, SFP Fiber transceiver (SFP.0LC.212.B0)
z1000Mbps BiDi SC, type 1, SM 20km, SFP Fiber WDM transceiver
(SFP.0BS.621.201)
z1000Mbps BiDi SC, type 2, SM 20km, SFP Fiber WDM transceiver
(SFP.0BS.621.202)
z1000Mbps LC, SM 10km, SFP Fiber transceiver with DDM (SFP.DLC.212.10)
Front View of 1000Base-SX/LX LC, SFP Fiber Transceiver
Front View of 1000Base-LX BiDi LC, SFP Fiber Transceiver

VigorSwitch G1240 User’s Guide
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1
1. .4 4 L LE ED D I In nd di ic ca at to or rs s a an nd d C Co on nn ne ec ct to or rs s
Before you use the Vigor device, please get acquainted with the LED indicators and
connectors first.
There are 24 TP Fast Ethernet ports and 2 slots for optional removable modules on the
front panel of the switch. LED display area, locating on the front panel, contains a ACT,
Power LED and 26 ports working status of the switch.
L
LE ED D E Ex xp pl la an na at ti io on n
LED Color Explanation
PWR Green
Lit when +3.3V power is coming up
10/100/1000Ethernet TP Port 1 to 24 LED
LINK/ACT Green Lit when connection with remote device is
good
Blinks when any traffic is present
LAN P1 – P24
(10/100/1000Mbps)
Green/
Amber
Lit Green when TP link on 1000Mbps speed
Lit Amber when TP link on 100Mbps speed
Off when 10Mbps or no link occur
Blinks when any traffic is present
1000SX/LX Gigabit Fiber Port 21, 22, 23, 24 LED
SFP(LINK/ACT) Green Lit when SFP connection with remote
device is good
Blinks when any traffic is present
C
Co on nn ne ec ct to or r E Ex xp pl la an na at ti io on n
Interface Description
RESET Used to restart the management system.
LAN P1 – P24 Giga Ethernet Port
SFP (21 – 24) SFP Fiber Port

VigorSwitch G1240 User’s Guide 5
U
Us se er r I In nt te er rf fa ac ce es s o on n t th he e R Re ea ar r P Pa an ne el l
(
24-PORT GBE WEB SMART SWITCH
1
1. .5 5 H Ha ar rd dw wa ar re e I In ns st ta al ll la at ti io on n
At the beginning, please do first:
¾Wear a grounding device to avoid the damage from electrostatic discharge
¾Be sure you have inserted the power cord to power source
1
1. .5 5. .1 1 C Co on nn ne ec ct ti in ng g t th he e S SF FP P F Fi ib be er r T Tr ra an ns sc ce ei iv ve er r t to o t th he e C
Ch ha as ss si is s
The optional SFP modules are hot swappable, so you can plug or unplug it before or after
powering on.
1. Verify that the SFP module is the right model and conforms to the chassis
2. Slide the module along the slot. Also be sure that the module is properly seated against
the slot socket/connector
3. Install the media cable for network connection
4. Repeat the above steps, as needed, for each module to be installed into slot(s)
5. Have the power ON after the above procedures are done
T
TP P P Po or rt t a an nd d C Ca ab bl le e I In ns st ta al ll la at ti io on n
In the switch, TP port supports MDI/MDI-X auto-crossover, so both types of cable,
straight-through (Cable pin-outs for RJ-45 jack 1, 2, 3, 6 to 1, 2, 3, 6 in 10/100M TP; 1, 2,
3, 4, 5, 6, 7, 8 to 1, 2, 3, 4, 5, 6, 7, 8 in Gigabit TP) and crossed-over (Cable pin-outs for
RJ-45 jack 1, 2, 3, 6 to 3, 6, 1, 2) can be used. It means you do not have to tell from them,
just plug it.
1. Use Cat. 5 grade RJ-45 TP cable to connect to a TP port of the switch and the other
end is connected to a network-aware device such as a workstation or a server.
2. Repeat the above steps, as needed, for each RJ-45 port to be connected to a Gigabit
10/100/1000 TP device.
3. Now, you can start having the switch in operation.
P
Po ow we er r O On n
The switch supports 100-240 VAC, 50-60 Hz power supply. The power supply will
automatically convert the local AC power source to DC power. It does not matter whether
any connection plugged into the switch or not when power on, even modules as well. After
the power is on, all LED indicators will light up immediately and then all off except the
power LED still keeps on. This represents a reset of the system.

VigorSwitch G1240 User’s Guide
6
F
Fi ir rm mw
wa ar re e L Lo oa ad di in ng g
After resetting, the bootloader will load the firmware into the memory. It will take about 30
seconds, after that, the switch will flash all the LED once and automatically performs
self-test and is in ready state.
1
1. .5 5. .2 2 I In ns st ta al ll li in ng g O Op pt ti io on na al l S SF FP P F Fi ib be er r T Tr ra an ns sc ce ei iv ve er rs s t to
o t th he e s sw wi it tc ch h
If you have no modules, please skip this section.
1
1. .5 5. .3 3 I In ns st ta al ll li in ng g C Ch ha as ss si is s t to o a a 1 19 9- -I In nc ch h W Wi ir ri in ng g C Cl lo os se et
t R Ra ai il l
Caution: Allow a proper spacing and proper air ventilation for the cooling fan at both
sides of the chassis.
1. Wear a grounding device for electrostatic discharge.
2. Screw the mounting accessory to the front side of the switch.
3. Place the Chassis into the 19-inch wiring closet rail and locate it at the proper position.
Then, fix the Chassis by screwing it.
1
1. .5 5. .4 4 C Ca ab bl li in ng g R Re eq qu ui ir re em me en nt ts s
To help ensure a successful installation and keep the network performance good, please
take a care on the cabling requirement. Cables with worse specification will render the
LAN to work poorly.
C
Ca ab bl li in ng g R Re eq qu ui ir re em me en nt ts s f fo or r T TP P P Po or rt ts s
For Fast Ethernet TP network connection

VigorSwitch G1240 User’s Guide 7
¾The grade of the cable must be Cat. 5 or Cat. 5e with a maximum length of 100
meters.
Gigabit Ethernet TP network connection
¾The grade of the cable must be Cat. 5 or Cat. 5e with a maximum length of 100
meters. Cat. 5e is recommended.
C
Ca ab bl li in ng g R Re eq qu ui ir re em me en nt ts s f fo or r 1 10 00 00 0S SX X/ /L LX X S SF FP P M Mo od du ul le e
It is more complex and comprehensive contrast to TP cabling in the fiber media. Basically,
there are two categories of fiber, multi mode (MM) and single mode (SM). The later is
categorized into several classes by the distance it supports. They are SX, LX, LHX, XD,
and ZX. From the viewpoint of connector type, there mainly are LC and BIDI LC.
¾Gigabit Fiber with multi-mode LC SFP module
¾Gigabit Fiber with single-mode LC SFP module
¾Gigabit Fiber with BiDi LC 1310nm SFP module
¾Gigabit Fiber with BiDi LC 1550nm SFP module
The following table lists the types of fiber that we support and those else not listed here are
available upon request.
Multi-mode Fiber Cable and Modal Bandwidth
Multi-mode 62.5/125μm Multi-mode 50/125μm
Modal Bandwidth Distance Modal Bandwidth Distance
160MHz-Km 220m 400MHz-Km 500m
IEEE 802.3z
Gigabit Ethernet
1000SX 850nm
200MHz-Km 275m 500MHz-Km 550m
Single-mode Fiber 9/125μm
Single-mode transceiver 1310nm 10Km
1000Base-LX/LH
X/XD/ZX Single-mode transceiver 1550nm 30, 50Km
TX(Transmit) 1310nm
Single-Mode *20Km RX(Receive) 1550nm
TX(Transmit) 1550nm
1000Base-LX
Single Fiber
(BIDI LC) Single-Mode *20Km RX(Receive) 1310nm
S
Sw wi it tc ch h C Ca as sc ca ad di in ng g i in n T To op po ol lo og gy y
Takes the Delay Time into Account
Theoretically, the switch partitions the collision domain for each port in switch cascading
that you may up-link the switches unlimitedly. In practice, the network extension
(cascading levels & overall diameter) must follow the constraint of the IEEE
802.3/802.3u/802.3z and other 802.1 series protocol specifications, in which the limitations
are the timing requirement from physical signals defined by 802.3 series specification of
Media Access Control (MAC) and PHY, and timer from some OSI layer 2 protocols such
as 802.1d, 802.1q, LACP and so on.
The fiber, TP cables and devices’ bit-time delay (round trip) are as follows:
1000Base-X TP, Fiber 100Base-TX TP/100Base-FX Fiber
Round trip Delay: 4096 Round trip Delay: 512

VigorSwitch G1240 User’s Guide
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Cat. 5 TP Wire: 11.12/m Cat. 5 TP Wire: 1.12/m Fiber Cable: 1.0/m
Fiber Cable: 10.10/m TP to fiber Converter: 56
Bit Time unit: 1ns (1sec./1000 Mega bit) Bit Time unit: 0.01μs (1sec./100 Mega bit)
Sum up all elements’ bit-time delay and the overall bit-time delay of wires/devices must be
within Round Trip Delay (bit times) in a half-duplex network segment (collision domain).
For full-duplex operation, this will not be applied. You may use the TP-Fiber module to
extend the TP node distance over fiber optic and provide the long haul connection.
Typical Network Topology in Deployment
A hierarchical network with minimum levels of switch may reduce the timing delay
between server and client station. Basically, with this approach, it will minimize the
number of switches in any one path; will lower the possibility of network loop and will
improve network efficiency. If more than two switches are connected in the same network,
select one switch as Level 1 switch and connect all other switches to it at Level 2.
Server/Host is recommended to connect to the Level 1 switch. This is general if no VLAN
or other special requirements are applied.
Case 1: All switch ports are in the same local area network.
Every port can access each other.
If VLAN is enabled and configured, each node in the network that can communicate each
other directly is bounded in the same VLAN area.
Here VLAN area is defined by what VLAN you are using. The switch supports both
port-based VLAN and tag-based VLAN. They are different in practical deployment,
especially in physical location. The following diagram shows how it works and what the
difference they are.

VigorSwitch G1240 User’s Guide 9
Case 2: Port-based VLAN -1
zThe same VLAN members could not be in different switches.
zEvery VLAN members could not access VLAN members each other.
zThe switch manager has to assign different names for each VLAN groups
at one switch.
Case 3: Port-based VLAN - 2
zVLAN1 members could not access VLAN2, VLAN3 and VLAN4 members.
zVLAN2 members could not access VLAN1 and VLAN3 members, but they could
access VLAN4 members.
zVLAN3 members could not access VLAN1, VLAN2 and VLAN4.

VigorSwitch G1240 User’s Guide
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zVLAN4 members could not access VLAN1 and VLAN3 members, but they could
access VLAN2 members.
Case 4: The same VLAN members can be at different switches with the same VID

VigorSwitch G1240 User’s Guide 11
1
1. .5 5. .5 5 C Co on nf fi ig gu ur ri in ng g t th he e M Ma an na ag ge em me en nt t A Ag ge en nt t o of f S Sw wi it tc ch h
Users can monitor and configure the switch through the following procedures.
Configuring the ManagementAgent of VigorSwitch G1240 through the Ethernet Port
There are two ways to configure and monitor the switch through the switch’s Ethernet port.
They are Web browser and SNMP manager. We just introduce the first type of
management interface. Web-based UI for the switch is an interface in a highly friendly
way.
Managing VigorSwitch G1240 through Ethernet Port
Before start using the switch, the IP address setting of the switch should be done, then
perform the following steps:
1. Set up a physical path between the configured the switch and a PC by a qualified UTP
Cat. 5 cable with RJ-45 connector.
Note: If PC directly connects to the switch, you have to setup the same subnet mask
between them. But, subnet mask may be different for the PC in the remote site.
Please refer to Fig. 2-6 about the 24-Port GbE Web Smart Switch default IP address
information.
2. Run web browser and follow the menu. Please refer to Chapter 2.

VigorSwitch G1240 User’s Guide
12
1
1. .5 5. .6 6 I IP P A Ad dd dr re es ss s A As ss si ig gn nm me en nt t
For IP address configuration, there are three parameters needed to be filled in. They are IP
address, Subnet Mask, Default Gateway and DNS.
IP address:
The address of the network device in the network is used for internetworking
communication. Its address structure looks is shown below. It is “classful” because it is
split into predefined address classes or categories.
Each class has its own network range between the network identifier and host identifier in
the 32 bits address. Each IP address comprises two parts: network identifier (address) and
host identifier (address). The former indicates the network where the addressed host resides,
and the latter indicates the individual host in the network which the address of host refers to.
And the host identifier must be unique in the same LAN. Here the term of IP address we
used is version 4, known as IPv4.
Network identifier Host identifier
32 bits
With the classful addressing, it divides IP address into three classes, class A, class B and
class C. The rest of IP addresses are for multicast and broadcast. The bit length of the
network prefix is the same as that of the subnet mask and is denoted as IP address/X, for
example, 192.168.1.0/24. Each class has its address range described below.
Class A:
Address is less than 126.255.255.255. There are a total of 126 networks can be defined
because the address 0.0.0.0 is reserved for default route and 127.0.0.0/8 is reserved for
loopback function.
Class B:
IP address range between 128.0.0.0 and 191.255.255.255. Each class B network has a
16-bit network prefix followed 16-bit host address. There are 16,384 (2^14)/16 networks
able to be defined with a maximum of 65534 (2^16 –2) hosts per network.
Class C:
IP address range between 192.0.0.0 and 223.255.255.255. Each class C network has a
24-bit network prefix followed 8-bit host address. There are 2,097,152 (2^21)/24 networks
able to be defined with a maximum of 254 (2^8 –2) hosts per network.

VigorSwitch G1240 User’s Guide 13
Class D and E:
Class D is a class with first 4 MSB (Most significance bit) set to 1-1-1-0 and is used for IP
Multicast. See also RFC 1112. Class E is a class with first 4 MSB set to 1-1-1-1 and is used
for IP broadcast.
According to IANA (Internet Assigned Numbers Authority), there are three specific IP
address blocks reserved and able to be used for extending internal network. We call it
Private IP address and list below:
Class A 10.0.0.0 --- 10.255.255.255
Class B 172.16.0.0 --- 172.31.255.255
Class C 192.168.0.0 --- 192.168.255.255
Please refer to RFC 1597 and RFC 1466 for more information.
Subnet mask:
It means the sub-division of a class-based network or a CIDR block. The subnet is used to
determine how to split an IP address to the network prefix and the host address in bitwise
basis. It is designed to utilize IP address more efficiently and ease to manage IP network.
For a class B network, 128.1.2.3, it may have a subnet mask 255.255.0.0 in default, in
which the first two bytes is with all 1s. This means more than 60 thousands of nodes in flat
IP address will be at the same network. It’s too large to manage practically. Now if we
divide it into smaller network by extending network prefix from 16 bits to, say 24 bits,
that’s using its third byte to subnet this class B network. Now it has a subnet mask
255.255.255.0, in which each bit of the first three bytes is 1. It’s now clear that the first two
bytes is used to identify the class B network, the third byte is used to identify the subnet
within this class B network and, of course, the last byte is the host number.
Not all IP address is available in the sub-netted network. Two special addresses are
reserved. They are the addresses with all zero’s and all one’s host number. For example, an
IP address 128.1.2.128, what IP address reserved will be looked like? All 0s mean the
network itself, and all 1s mean IP broadcast.

VigorSwitch G1240 User’s Guide
14
In this diagram, you can see the subnet mask with 25-bit long, 255.255.255.128, contains
126 members in the sub-netted network. Another is that the length of network prefix equals
the number of the bit with 1s in that subnet mask. With this, you can easily count the
number of IP addresses matched. The following table shows the result.
Prefix Length No. of IP matched No. of Addressable IP
/32 1 -
/31 2 -
/30 4 2
/29 8 6
/28 16 14
/27 32 30
/26 64 62
/25 128 126
/24 256 254
/23 512 510
/22 1024 1022
/21 2048 2046
/20 4096 4094
/19 8192 8190
/18 16384 16382
/17 32768 32766
/16 65536 65534
According to the scheme above, a subnet mask 255.255.255.0 will partition a network with
the class C. It means there will have a maximum of 254 effective nodes existed in this
sub-netted network and is considered a physical network in an autonomous network. So it
owns a network IP address which may looks like 168.1.2.0.
With the subnet mask, a bigger network can be cut into small pieces of network. If we want
to have more than two independent networks in a worknet, a partition to the network must
be performed. In this case, subnet mask must be applied.
For different network applications, the subnet mask may look like 255.255.255.240. This
means it is a small network accommodating a maximum of 15 nodes in the network.
Default gateway:
For the routed packet, if the destination is not in the routing table, all the traffic is put into
the device with the designated IP address, known as default router. Basically, it is a routing
policy. The gateway setting is used for Trap Events Host only in the switch.
For assigning an IP address to the switch, you just have to check what the IP address of the
network will be connected with the switch. Use the same network address and append your
host address to it.