Forwarding issues related to MACs starting with a 4 or a 6 (Was: [c-nsp] Wierd MPLS/VPLS issue)

Saku Ytti saku at
Fri Dec 2 23:17:48 UTC 2016

On 2 December 2016 at 18:16, Alia Atlas <akatlas at> wrote:
> This sounds related to the well-known (at least 10+ years) issues around
> guessing the
> type of IP packet by looking at the first nibble of the encapsulated packet.
> Take a quick look at RFC 7325, section bullet 6.
> This is what using the pseudo-wire code-word is meant to protect against.
> I don't know if that's an option for networks using this.

Some devices by default look inside pseudowires to find IP inside
them, in this case even control-word won't help, you'll need to also
disable looking inside pseudowire.


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