1841 router with VLAN's

Unanswered Question
Sep 8th, 2008

Hello:

I have a 1841 router. I need to support 6 VLAN's. My plan is to use 2960 switches connected to the 1841 and configure the Ethernet port as a trunk port. I have searched but have not found anything on this type of config. Does anyone have any pointers or advice on the config?

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Jon Marshall Mon, 09/08/2008 - 08:47

1) Create your 6 vlans on 2960 switch eg

2960(config)# vlan 10

2960(config-vlan)# name v10

2960(config)# vlan 11

2960(config-vlan)# name v11

etc. for each vlan

2) On the port that connects the 2960 to your 1841 router

int fa0/1

switchport mode trunk

(no need to specify encapsulation as 2960 only supports 802.1q

3) On 1841

int fa0/0.10

encapsulation dot1q 10

ip address 192.168.5.1 255.255.255.0

int fa0/0.11

encapsulation dot1q 11

ip address 192.168.6.1 255.255.255.0

etc.. for each vlan.

Note that the interface number does not have to match the vlan number but the encapsulation dot1q must match the vlan number.

Jon

Giuseppe Larosa Mon, 09/08/2008 - 08:49

Hello Harrison,

if your 1841 hasn't an etherswitch module, you can use the old approach:

switch side: layer 2 trunk port with 6 vlans permitted using 802.1Q

router side: a FE/Ge port with:

no ip address on main interface

int fa0/0.30

encapsulation dot1q 30

ip address x.x.x.x 255.255.255.0

define 6 subinterfaces, the parameter in the enc dot1q command must match the desired vlan-id.

if you have an etherswitch module on the 1841 you can :

define the 6 vlans on the etherswitch

define 6 SVI interfaces associated to the 6 vlans (remenber the no shut)

define a l2 trunk for each 2960 carrying the 6 vlans

use this config guide as a reference

http://www.cisco.com/en/US/docs/ios/lanswitch/configuration/guide/12_4/lsw_12_4_bk.html

Hope to help

Giuseppe

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