Configure

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool ( registered customers only) .

Network Diagram

This document uses the network setup shown in the diagram below.

Configurations

This document uses the configurations shown below.

Note: Router models with certain network modules may have different minimum Cisco IOS versions that support ISL trunking.

• Catalyst 3512-XL

• Cisco 2600 Router

• 802.1Q Configuration on the Router for Cisco IOS Versions Earlier than 12.1(3)T

  switch#configure terminal

  Enter configuration commands, one per line. End with CNTL/Z.

  switch(config)#hostname 3512xl

  3512xl(config)#enable password mysecret

  3512xl(config)#line vty 0 4

  3512xl(config-line)#login

  3512xl(config-line)#password mysecret

  3512xl(config-line)#exit

  3512xl(config)#no logging console

  3512xl(config)#^Z

  !-- Set the IP address and default gateway for VLAN1 for management purposes.

  3512xl#configure terminal

  Enter configuration commands, one per line. End with CNTL/Z.

  3512xl(config)#int vlan 1

  3512xl(config-if)#ip address 10.10.10.2 255.255.255.0

  3512xl(config-if)#exit

  3512xl(config)#ip default-gateway 10.10.10.1

  3512xl(config)#end

  !-- Set the VTP Mode.

  !-- In our example, we have set the mode to be transparent.

  !-- Depending on your network, set the VTP Mode accordingly.

  !-- For details on VTP,

  !-- refer to

  !-- Creating and Maintaining VLANs on Catalyst 2900XL and 3500XL Switches.

  3512xl#vlan database

  3512xl(vlan)#vtp transparent

  Setting device to VTP TRANSPARENT mode.

  !-- Adding VLAN2. VLAN1 already exists by default.

  3512xl(vlan)#vlan 2

  VLAN 2 added:

  Name: VLAN0002

  3512xl(vlan)#exit

  APPLY completed.

  Exiting....

  !-- Enable trunking on the interface fastEthernet 0/1.

  3512xl#configure terminal

  Enter configuration commands, one per line. End with CNTL/Z.

  3512xl(config)#int fastEthernet 0/1

  3512xl(config-if)#switchport mode trunk

  !-- Enter the trunking encapsulation as either isl

  3512xl(config-if)#switchport trunk encapsulation isl

  !-- or as dot1q:

  3512xl(config-if)#switchport trunk encapsulation dot1q

  !-- In case of 2940/2950 series switches, none of the above two commands are used,

  !-- 2940/2950 series switches only support 802.1q encapsulation which is configured automatically,

  !-- when trunking is enabled on the interface by using switchport mode trunk command.

  !-- In case of dot1q, you need to make sure that

  !-- the native VLAN matches across the link.

  !-- On 3512XL, by default, the native VLAN is 1.

  !-- Depending on your network needs, you may change

  !-- the native VLAN to be other than VLAN1,

  !-- but it is very important that you change the native VLAN

  !-- on the router accordingly.

  !-- You may change the native VLAN, if needed, by using the following command:

  !-- 3512xl(config-if)#switchport trunk native vlan 

  !-- Allow all VLANs on the trunk.

  3512xl(config-if)#switchport trunk allowed vlan all

  3512xl(config-if)#exit

  !-- The following set of commands will place FastEthernet 0/2

  !-- into VLAN2 and enable portfast on the interface.

  3512xl(config)#int fastEthernet 0/2

  3512xl(config-if)#switchport access vlan 2

  3512xl(config-if)#spanning-tree portfast

  3512xl(config-if)#exit

  !-- FastEthernet 0/3 is already in VLAN1 by default.

  !-- Enable portfast on the interface.

  3512xl(config)#int fastEthernet 0/3

  3512xl(config-if)#spanning-tree portfast

  3512xl(config-if)#^Z

  !-- For details on why to enable portfast,

  !-- refer to:

  !-- Using PortFast and Other Commands to Fix Workstation Startup Connectivity Delays.

  !-- Remember to save the configuration.

  3512xl#write memory

  Building configuration...

  3512xl#

  --------------------------------------------------------------------------------

  3512xl#show running-config

  Building configuration...

  Current configuration:

  !

  version 12.0

  no service pad

  service timestamps debug uptime

  service timestamps log uptime

  no service password-encryption

  !

  hostname 3512xl

  !

  no logging console

  enable password mysecret

  !

  !

  !

  !

  !

  ip subnet-zero

  !

  !

  !

  interface FastEthernet0/1

    switchport mode trunk

  !

  !-- If 802.1Q is configured,

  !-- you will instead see the following output

  !-- under interface FastEthernet0/1:

  !-- interface FastEthernet0/1

  !-- switchport trunk encapsulation dot1q

  !-- switchport mode trunk

  !

  interface FastEthernet0/2

   switchport access vlan 2

   spanning-tree portfast

  !

  interface FastEthernet0/3

   spanning-tree portfast

  !

  interface FastEthernet0/4

  !

  interface FastEthernet0/5

  !

  interface FastEthernet0/6

  !

  interface FastEthernet0/7

  !

  interface FastEthernet0/8

  !

  interface FastEthernet0/9

  !

  interface FastEthernet0/10

  !

  interface FastEthernet0/11

  !

  interface FastEthernet0/12

  !

  interface GigabitEthernet0/1

  !

  interface GigabitEthernet0/2

  !

  interface VLAN1

   ip address 10.10.10.2 255.255.255.0

   no ip directed-broadcast

   no ip route-cache

  !

  ip default-gateway 10.10.10.1

  !

  line con 0

   transport input none

   stopbits 1

  line vty 0 4

   password mysecret

   login

  line vty 5 15

   login

  !

  end