Extending Vlan over L3 link

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Sep 16th, 2009
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I have two Multilayer switches in my campus.

One is a cisco 6509 with Sup 720 and the other is a Cisco 4006 with sup IV.

I have a 3 Link between the two switches.

One Switches hosts subnets in the 172.16.X.X network and the other 172.17.X.X.

Now my requirement is , i have a vlan with say in the cisco 6509 where i am hosting a few servers.

I have one more server connected to the cisco 4006 switch.

For some experimental reason i need the server connected to the 4006 to be in the same subnet

i cannot change the L3 Link to a L2 Link and trunk it.

is there any other tunnel technique or something to make this possible.

Please be aware of the hardware and IOS limitations.

The 6509 has the latest and the greatest but the 4006 with the Sup IV has the 12.2 IOS which is the latest available.

Also i dont think the 6509 as well supports the Pseudowire etc stuff.

Please help

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Giuseppe Larosa Wed, 09/16/2009 - 06:12
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Hello Victor,

given your HW especially the 4006 sup IV I think that only L2 trunking is a viable solution.

Between two ISR routers you could use L2TPv3 but I don't think 4006 supports it.

A possible workaround would be to use NAT on C6509 sup720 to make the server appears as having an ip address in net

But this doesn't emulate a single vlan.

Hope to help


victor_87 Wed, 09/16/2009 - 06:20
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Hi Guiseppe,

Thanks for the quick reply. I am a network engineer and do not have access to the server and the Ip address on the server is already set to something in the subnet.

Now my task is to make the Server reachable from the 6500 without changing any server side settings, nevermind if it is not reachable from other subnets in the 4006 where it is physically connected.

rducombl Wed, 09/16/2009 - 06:35
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Indeed there is no way beside layer 2 between 4k and 6500 to achieve that.

4500 supIV do not support neither Pseudowire (EomPls) , neither l2tpv3.



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