Extending Networks over L3

Unanswered Question
Nov 6th, 2008


I'm trying to get different options on a way to bridge two networks in different sites. Basically I have two locations that need to extend VLAN(s) with about 15ms latency between them.

1. My questions what are the options?

2. Does anyone know of any performance effect this could have?

I know I could do a BVI, but to my best knowledge that would only bridge one VLAN (I would need multiple vlans).

I was trying to avoid bridging a GRE tunnel (extra overhead), but I think that's another way to do this.

Is there other method I'm missing?

Thank you in advance.

I have this problem too.
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tomek0001 Thu, 11/06/2008 - 10:26


I think that QinQ would only work for switches (to the best of my knowledge), in this case i'm looking for something on the routers.

tomek0001 Thu, 11/06/2008 - 10:24


This would be running on a 3845 with an OC-3 link. Would you say that L2 MPLS is better suited for this? Would L2TPv3 introduce delay on such a link?

Thank you,

Giuseppe Larosa Thu, 11/06/2008 - 11:10

Hello Tomasz,

all depends from the traffic volume you need to transfer that depends from applications or other needs like Disaster recovery.

If an asynch mirroring is what is asked (and this is the only choice if the two sites are more distant then 200 km) an OC-3 can be good.

If the requirements are higher I would go to an EoMPLS solution instead of building a L2TPv3 solution with two 6500 with Sup720 and you could use cheaper LAN switches as your CPE devices.

Hope to help



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