Routing over a Trunk

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Apr 17th, 2008
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Suppose I have 2 core switches at seperate locations with a GiG ethernet connection between the switches. Right now the GiG Ethernet connection is configured as a dot1q trunk which is required to carry a vendor's Layer 2 proprietary traffic between sites.

The issue i'm facing now is if we wanted to route traffic (i.e OSPF routes) over the trunk for other application how would I do that?

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Istvan_Rabai Thu, 04/17/2008 - 21:32
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Hi Milan,

If you want this trunk to remain a layer2 trunk, you can use the vlan interfaces belonging to the vlans allowed on this trunk to route traffic.

E.g. your trunk carries vlans 2 and 3, then you can configure the vlan interfaces like this:

interface vlan 2

ip address x.x.x.x x.x.x.x

interface vlan 3

ip address y.y.y.y y.y.y.y

Then you can use the ip addresses of these interfaces in your ospf configuration with the "network" ospf router command.

If you provide more info about your current and expected configurations, then I can give you a more specific answer.



kapish.mohole Thu, 04/17/2008 - 22:26
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That is right, you can create vlan layer 3 interfaces and do routing.

If you dont want vlan interfeaces and routing to happen in your desired vlans and other vlans then use loopback and gre tunnel combination to pass routing information.



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