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Community Member

vlans across a wan

I have the following configuration in a lab environment.

SWITCH A  (vlan 2, vlan 3)
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RouterA (10.0.0.2 (wan), 192.168.0.1 (lan))
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RouterB (10.0.0.1 (wan), 192.168.1.1 (lan))
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SWITCH B (vlan 3)

How do I get users on vlan 3 on switch B to talk to
users on vlan 2 and vlan3 on switch A.
SWitch A and B are layer 3 switches
1) Is trunking needed ? IF so, where ?
2) Do I need to assign ip addresses to each vlan interface?
   If so, what can these ip's be ?

11 REPLIES

Re: vlans across a wan

Hi,

If you just want users one one side to talk to users on the other side you can accomplish that with routing.

On the other hand,  if you're looking to pass VLAN information through the WAN then there some methods of doing this like L2TPv3 and QinQ.

It all depends on what you want to do.

Federico.

Cisco Employee

Re: vlans across a wan

Hi,

You can do it with routing.

You need to configure int vlan and enable routing.

SW1-----vlan2,192.168.0.0/24---R1----10.0.0.0/24-----R2----192.168.1.0/24,vlan3-----SW2

on SW1

int vlan 2

ip add 192.168.0.x 255.255.255.0

router eigrp 1

no auto

net 192.168.0.0 0.0.0.255

on R1 and R2

router eigrp 1

no auto

net 0.0.0.0 0.0.0.0

on SW2

on SW1

int vlan 3

ip add 192.168.1.x 255.255.255.0

router eigrp 1

no auto

net 192.168.1.0 0.0.0.255

KK

Community Member

Re: vlans across a wan

why do i not need to make the links between router and switches trunk links ?

On Mon, Aug 30, 2010 at 12:27 PM, kyukim

Community Member

Re: vlans across a wan

and also, does vlan 3 need to be in different ip subnets on both switches ?

Re: vlans across a wan

Whenever the switch is handling more than a single VLAN (two or more), then the connection between the switch and the router should be a trunk.

VLAN 3 should be a different IP subnet on both sides to avoid overlapping (unless you use NAT).

Federico.

Community Member

Re: vlans across a wan

so you are saying that if i had vlan 2, 3, on switch A, and vlan 2, 3

on switch B, then the links to the router from each switch would need

to be trunk links right ?

On Mon, Aug 30, 2010 at 1:54 PM, coto.fusionet

Re: vlans across a wan

If you have VLAN 2, 3 on switch A and VLAN 2,3 on switch B (assuming they are Layer 2 switches and the Inter-VLAN routing is been done by the router on each end..)

then yes...

the connection between the switches and routers should be trunk.

Federico.

Community Member

Re: vlans across a wan

no in my case the switches are layer 3 and intervlan routing is on the switches

On Mon, Aug 30, 2010 at 2:02 PM, coto.fusionet

Re: vlans across a wan

Then,

If you have a Layer 3 connection between the switches and the routers, there's no Trunk concept (the connection is just a Layer 3 connection).

Or if you're using a Layer 2 connection to the router, then it don't have to be a trunk (because the InterVLAN is handled by the switch).

Federico.

Community Member

Re: vlans across a wan

So last question.. lets say on switch A, vlan 2 interface has ip

192.168.0.2 /24 and can communicate with the router A on 192.168.0.1

/24

Vlan 3 interface on switch A has a different range eg. 192.168.3.1.

Then how will vlan 3 interface communicate with the router?

Would traffic originating from vlan 3 first go to the vlan 2 interface

then to the router ?

On Mon, Aug 30, 2010 at 2:11 PM, coto.fusionet

Re: vlans across a wan

You have

VLAN 2 192.168.0.0/24

VLAN 3 192.168.3.0/24

The router has an interface 192.168.0.1

You mentioned that the Layer 3 switch is doing the InterVLAN routing, if so, then the Layer 3 switch should have two SVIs.

interface vlan 2

ip add 192.168.0.2 255.255.255.0

interface vlan 3

ip add 192.168.3.x 255.255.255.0

Then, all the communication between the switch and the router goes through the 192.168.0.0/24 connection.

This is not the only way to do it, but I assume that's how you have it.

Federico.

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