How to extend VLANs across WAN link

20 pts.
InterVLAN Routing
VLAN configuration
How do I extend 2 vlans over a WAN link. I'm using 2 routers and simulated the WAN by connecting 2 paradyne modems back to back with a cross cable. both routers are seeing each other. switch-> router1->modem->modem->router2->workstations. I need to be able to see the vlans on router 2 and to run applications on workstation

Software/Hardware used:
cisco 2621xm routers

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Sorry this will be vague, but basically i believe you would set up the interfaces as trunks and allow the vlans you want to traverse you connection. One would probably use 802.1Q encapsulation / tagging and depending on the ios version, you might also have to declare a native vlan for the vlan tagged traffic to travel on. Also assuming you are using some sort of switch to connect your end points to router, the same would be needed for the connected port to the router say something like switchport mode trunk on the port connected to the router and the workstation port would have something like switchport mode access and switchport access vlanx as part of the configuration for that particular port..


Well this is actually a test situation, I know it’s not recommended, I have configured the first router, and configured the vlans on the router using dot1q encapsulation, what I wanted to know is how to configure the second router to seethe vlans and so the workstation can access those vlans after they come through the second router


I agree with Saturno / Labnuke: You would just basically set-up the same VLANs on both sites – routers switches and the like. With VLAN tagging, the devices would sort through the traffic and funnel it appropriately.

Short answer: set up both “LANs” with identical VLAN info…

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  • Labnuke99
    hmmm... well VLAN's are typically a broadcast domain, you don't want broadcasts to traverse a WAN and also the name says Virtual Local Area Network - for what purpose would you have a VLAN across a WAN link?
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  • saturno
    I tend to agree with Labnuke99 that what you're trying to do might not be the best approach to your intentions. Also, you do not need VLAN's to access each site/branch office applications, shared files/folders, etc... Even so, what you're trying to do is feasible. The key points to achieve that scenario is to have both routers and switches in each site correctly configured. Routers with all sub-interfaces for each VLAN and switches with port trunk's configured in at least each router connected port. If this is not enough, please clarify a little further. Luís
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