Stretch VLAN across WAN

Unanswered Question
Aug 21st, 2008

I have a DR site in another city, 90 miles away, connected via AT&T MPLS connection. Anyway to stretch a VLAN across sites??

I have this problem too.
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trippi Thu, 08/21/2008 - 09:03

without having a 7200 series router to do L2TPv3...

I have 2821s...

Or is this something I can get from AT&T..

Giuseppe Larosa Thu, 08/21/2008 - 10:24

Hello Andy,

>> Or is this something I can get from AT&T..

yes, just ask for an EoMPLS service that is L2VPN service over MPLS is the best choice to avoid performance issues.

I used L2TPv3 on C3725 or C3745, I don't know for 2821 try using feature navigator

I've checked basic L2tpv3

for example:

12.4(20)T ADVANCED ENTERPRISE SERVICES WITH SNA SWITCHING c2800nm-adventerprisek9_sna-mz.124-20.T.bin

this requires 256MB RAM and 64 MB flash

Hope to help


trippi Thu, 08/21/2008 - 11:57

EoMPLS is different from the MPLS connection I have now? Or would I just need to update the IOS to one that supports L2TPV3 and run?

Giuseppe Larosa Thu, 08/21/2008 - 12:20

Hello Andy,

EoMPLS is a different service from L3 VPN so it requires to buy a new service from your provider with a different access link on each side. Price should be low but however it adds to current expenses.

Otherwise you can try with L2TPv3 on the CE routers, the question is how much traffic do you expect on this DR service ?

I'm afraid 2821 cannot handle high volume traffic over L2TPv3.

Hope to help


J2NoomSai_2 Thu, 08/21/2008 - 13:09


I also have a question for stretch VLAN. I have ptp between two sites and how can I strectch the vlan from one site to another site. BTW, I have cisco 2691 router.



Giuseppe Larosa Fri, 08/22/2008 - 06:08

Hello Sai,

if you have a Frame-Relay point-to-point link you can use bridging over the WAN.

Be aware that all broadcast traffic will be bridged and will consume bandwidth

bridge 1 protocol ieee

bridge 1 route ip

int eth0/0

bridge-group 1

int ser0/0

enc frame-relay

int ser0/0.100 point-to-point

frame-rel interface-dlci 100

bridge-group 1

ip address

interface BV1

ip address

desc l3 interface for Vlan over two sites

the same must be done on the other router

Hope to help

Giuseppe Larosa

J2NoomSai_2 Fri, 08/22/2008 - 07:40

Thanks Guiseppe

I have 2xT1 with multilink. Is that going to work the same configuration? This is my first time for this kind of task. Thanks in advance.


Edison Ortiz Fri, 08/22/2008 - 08:47


I strongly recommend against extending your broadcast domain over a 3Mbps unreliable WAN link. Some odd results can occur in your network.

I'm sure your requirement can be met in a routed network. I haven't seen a design that calls for extending Vlan over a slow WAN. Yes, I'm aware of some Microsoft products that require services to be in the same LAN but I'm sure there are ways to make it work over a routed network.




awatkins Fri, 08/22/2008 - 23:44

If this needs to be done, then I would use an l2tpv3 psuedowire on the routers at each end of your MPLS cloud.

We do this occationally in customer nets where they need effectively a l2 vlan spanned accross sites.

you'll want a dot1q int on each router with no local ip address and set up Xconnect over the IP MPLS cloud.

trippi Wed, 11/26/2008 - 07:38

Am I able to do this with a new dot1q subinterface? I don't want to impact the existing routed traffic. I just want to add this subnet to this location without removing the other different existing subnets.


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