Layer2 over Layer3

Mike Jones mike at mikejones.in
Thu Sep 13 20:32:35 UTC 2012


On 12 September 2012 23:23, Philip Lavine <source_route at yahoo.com> wrote:
> To all,
>
> I am trying to extend a layer2 connection over Layer 3 so I can have redundant Layer connectivity between my HQ and colo site. The reason I need this is so I can give the "appeareance" that there is one gateway and that both data centers can share the same Layer3 subnet (which I am announcing via BGP to 2 different vendors).
>
> I have 2 ASR's. Will EoMPLS work or is there another option?
>
> Philip

Depending on your specific requirements, if you simply want to be able
to address hosts out of the same subnet and don't need actual layer 2
connectivity you might also want to consider proxy ARP(+NDP). This
trades some issues for others, for example you don't need to worry
about MTU issues, but it won't forward broadcast packets (this could
be either an advantage or disadvantage) or non-IP packets, it also
requires you to configure the routers so they know which addresses are
at the other site. Lots of disadvantages but there are situations
where it might be an option.

- Mike



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