Layer 2 across Layer 3

[John Crubaugh]

Is it possible to pass layer 2 traffic across a layer 3 link between a Catalyst 4500 and Catalyst 6500.  I basically have OSPF connection between the 2 devices but need to extend the same subnet across both devices. I don't have any more physical connections or budget for more hardware..

Inquiring minds want to know.

[Joseph W. Doherty]

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Posting

Well you could do that across a VLAN trunk while also having L3 across the same link too.  The latter could be done using a "p2p" VLAN.

[Ashok Kumar]

Hi,

Theoretically Yes! even practically but not sure if it 's suit your environment.

Below is very configuration example to GRE/L2TP:

http://www.cisco.com/c/en/us/support/docs/ip/layer-two-tunnel-protocol-l2tp/116266-configure-l2-00.html

- Ashok

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[John Crubaugh]

only problem is this ..

• The L3 tunneling encapsulation depends on the device that does the tunneling:
  1. Cisco 7301 supports L2TPv3 encapsulation.
  2. Cisco 65xx does not support L2 extension with the L2TPv3 tunnel. However, the L2 can be extended across an MLPS core with the Any Transport over MPLS (AToM) option.
  3. The L2TP tunnel is not supported on the Cisco 4500 switches

I had found that link too but was disappointed when i read this. :(