Ethernet extension / Bridging an L2 network across an L3 network is to use L2TPv3

[AlexFer]

Hello experts,

my requirement is to extend a VLAN across L3 network. The access L3 switches are Catalyst 3850.

I have found L2 Bridging Across an L3 Network Configuration Example that seems to fit the bill. However, I couple of questions:

1. What's the significance of "As with the GRE tunneling solution, the use of a router on which to terminate the L2 tunnel still does not allow L2 Protocol Data Unit (PDU) messages to be forwarded across the tunnel. Without proper L2 protocol tunneling, which is not supported on a router, these messages are consumed by the L2 interface" caveat?

2. Can the Xconnect interface be an SVI interface instead of a physical (or sub-interface)? If not, how can I define default gateway for the hosts on the VLAN being extended?

Thank you. Alex.

[balaji.bandi]

If you are using Public network bridging network and requirement to be extend Lan  using L2TPv3  ( GRE tunnel does not give any security protection)

Xconnect generally used by MPLS Service provider ? are you using MPLS network ? what device model ? Xonnect do support sub interface again depends on the model and device.

[MHM Cisco World]

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[AlexFer]

Hi Experts,

reading up more on Cisco L2TPv3/Xconnnect implementation, the answer to my questions:

2. Can the Xconnect interface be an SVI interface instead of a physical (or sub-interface)? If not, how can I define default gateway for the hosts on the VLAN being extended?

Seems to be "no", and for latter, seems, I'd need to utilise a two physical connections - first for attachment circuit, and second, for the SVI. I guess I could use a trunk to combine two.

To clarify, our access layer 3850 L3 switches' upstream interfaces are all routed (ie. all VLANs are confined to the switch).

Would appreciate expert advice, or, best-practice advice, or alternative to L2TPv3 for VLAN extension.

Thanks, Alex.