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New Member

Tagged 802.1Q VLANs over frame relay ?

Subject: Tagged 802.1Q VLANs over frame relay ?

Can a Cisco 1720 router pass 802.1Q tagged VLANs over Frame Relay to a Cisco 2651 router?

I have some 802.1Q tagged VLANs between a Cisco 2651 router and a Cisco 3550-48 switch. Everything is working great.

I now want to pass 802.1Q tagged VLANs from my Cisco 2651 router over a T1 Frame Relay to an off site Cisco 1720 router and then add a Cisco 3550-48 switch on the FastEthernet interface of my Cisco 1720 router.

[2651 -- Serial0/0.16

Can this be done?

If not, can I bridge 802.1Q traffic over a Frame Relay interface of my Cisco 2651 to my Cisco 1720 so that I end up with tagged 802.1Q VLAN traffic on the FastEthernet interface of my Cisco 1720?

Does anybody know where I can find some documentation on passing 802.1Q tagged VLAN information over Frame Relay?

Thanks

Tom Jones

3 REPLIES
New Member

Re: Tagged 802.1Q VLANs over frame relay ?

Re: Tagged 802.1Q VLANs over frame relay ?

Hi,

You'll need the 1721 like Bruce mentioned, but you can't do 802.1Q over frame relay directly. There are workarounds but why not just route between the sites and give each LAN it's own IP subnet ?

The workaround would be to use a point-to-point frame relay subinterface and have a bridge-group for each VLAN and bridge between the sites.

Sample config for this:

interface fa0/0.10

description vlan 10

encaps dot1q 10 native

bridge-group 10

interface fa0/0.20

description vlan 20

encaps dot1q 20

bridge-group 20

intrface s0/0

encaps frame-relay

no shut

interface s0/0.10 point-to-point

frame-relay interface-dlci 16

no ip address

bridge-group 10

interface s0/0.20 point-to-point

frame-relay interface-dlci 17

no ip address

bridge-group 20

On core router, you would have same configuration as well as IRB to route between bridged networks and non-bridged networks.

bridge irb

bridge 10 route ip

bridge 20 route ip

bridge 10 protocol ieee

bridge 20 protocol ieee

interface bvi10

ip address 10.x.x.x y.y.y.y

interface bvi20

ip address 20.x.x.x y.y.y.y

New Member

Re: Tagged 802.1Q VLANs over frame relay ?

Thanks for the info.

RE: There are workarounds but why not just route between the sites and give each LAN it's own IP subnet ?

I normally would just route subnets, however I may need the ability for some vlans to have the same IP subnet at two different locations separated by the frame relay interface.

I kind of like the idea of using more than one DLCI and bridging, however each vlan would eat up a DLCI and I would not have the ability to quickly add vlans if needed.

As for the 1721, I may have to play with one of them and see what it can do that the 1720 cannot do.

I may have an idea to get me working - not sure however. I have another unused 1720 router. I may give this a trial run and see what happens:

* Have both 1720 routers bridge the LAN traffic over the Frame Relay.

* Connect the 1720 FE ports to tagged ports on 802.1q switches at both locations.

- - At this point, tagged Ethernet traffic may bridge between the 1720 routers - -

* Use the Console port on both 1720 routers so that I can get into them - or add a second Ethernet WIC to each 1720 and connect them to untagged ports on the switches.

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