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Webcast-Catalyst9k
rob
New Member

bridging 802.1q

Rather than using a Lan extension converter I was wondering if it was possible to still be able to use 802.1q after terminating the line on a router and then converting the router into a bridge. I was hoping to do this to get round the restrictions of distance on most of the Lan converters on the market today.

Many thanks

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: bridging 802.1q

It is possible to have an 802.1Q trunk between two switches via routers configured as a bridge. The router interfaces bridge and are not configured for 802.1Q. The catch is you may have to increase the MTU size to 1524 to allow large frames through ie. max ethernet frame plus 802.1Q bits.

SWITCH

| (802.1q trunk)

|

| (bridge interface)

ROUTER

: (bridge interface)

:

: (bridge interface)

ROUTER

| (bridge interface)

|

| (802.1q trunk)

SWITCH

Peter

3 REPLIES
Cisco Employee

Re: bridging 802.1q

The router interfaces would need to support dot1q and bridging of the subinterfaces. Did you have a specific platform in mind?

New Member

Re: bridging 802.1q

It is possible to have an 802.1Q trunk between two switches via routers configured as a bridge. The router interfaces bridge and are not configured for 802.1Q. The catch is you may have to increase the MTU size to 1524 to allow large frames through ie. max ethernet frame plus 802.1Q bits.

SWITCH

| (802.1q trunk)

|

| (bridge interface)

ROUTER

: (bridge interface)

:

: (bridge interface)

ROUTER

| (bridge interface)

|

| (802.1q trunk)

SWITCH

Peter

rob
New Member

Re: bridging 802.1q

Peter,

Many thanks..this is exactly what I was after

Thanks again

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