Extend VLAN Over WAN

Unanswered Question
Mar 10th, 2010

Hello Netpro

How to extended VLAN over WAN Link between PointA to PointB. Vlan121 was created on PointA, one Server at PointB needs to be on same LAN. WAN Link between PointA to PointB is over outdoor broadband wireless networks.



I have this problem too.
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Paolo Bevilacqua Wed, 03/10/2010 - 11:38

Which equipment the wireless is? If not cisco, or do not support VLAN, you are out of luck.

Paolo Bevilacqua Wed, 03/10/2010 - 12:05

Configure switchport connecting wireless as mode trunk.

Routers will not see that VLAN traffic at all.

However consider that most claims by application vendors of "need to be on the same subnet" are false.

Router can also help in getting things to work when they don't.

tomfree_leo Wed, 03/10/2010 - 12:12


what do u mean " Routers will not see that VLAN traffic at all "



Leo Laohoo Wed, 03/10/2010 - 13:08

Hi Tom,

Can you elaborate your issue?  Are you trying to get the Wireless Link working?

If this is so, I can't speak for other vendors, but what issues are you getting here?  How far apart are the two wirless bridge from each other?  Are they line-of-sight?  What antennae are you using?

tomfree_leo Thu, 03/11/2010 - 01:01


Wirelesss point 2 point is working.

Links is up, i want to extend VLAN.

Paolo Bevilacqua Thu, 03/11/2010 - 01:55

Are you the end user ? If yes,recommend you engage a professional network engineer to make this configuration, even if the issue is indeed very simple.

Otherwise, do not extend VLAN and you will see that application will perfectly work anyway.

wilson_1234_2 Thu, 03/11/2010 - 16:29

Mr. Bevilacqua,

Can you explain the problems you are talking about that are associated with extending a broadcast domain across a wan link?

For example, say there is a switch end to end extending a vlan as talked about in  this thread.

Are the broadcasts that much less efficient than routed packets would be going across?

Paolo Bevilacqua Fri, 03/12/2010 - 02:22

In this case it is possible to extend the VLAN because the circuit (Wireless) supports VLAN tagging.

Note generally spealing wireless linksa re considere LAN and not WAN.

When it does not, it is not possible to extend VLAN, but that is not a problem because things will work anyway.

So it is not a matter of broadcasts or not, but simply what is possible and what is not.

wilson_1234_2 Fri, 03/12/2010 - 05:44

Thanks for the reply,

If I remember correctly you are Paul (sorry if that is incorrect),

I was also thinking also of this thread:


You mentioned that you should never use subnets across a WAN to get professional results.

I have heard that numerous times and I am not sure exactly what the issue is with doing it.

Is it that the broadcasts will utilize a significant portion of the bandwidth?

Also, with switches, is there potential for multicast flooding across the link?

Paolo Bevilacqua Fri, 03/12/2010 - 05:51

That is not the case in discussion.

Wireless links are of LAN speed in most cases, and can carry VLAN without any problem.

WAN links are slow and separate locations on which there is no reason to extend VLAN, beside it is not readily possible to do that.

Leo Laohoo Thu, 03/11/2010 - 13:18

I can help you if your Wireless AP/Bridge is Cisco stuff because I've been doing a few of these.  But with other vendors (and I'm not being an a-hole here), I don't know what these can/can't do.  Sorry.  You'll have to go to the vendor of your Wireless AP/Bridge and ask them.


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