[j-nsp] BGP VPLS MTU for pseudowires

[Saku Ytti]

Hey Dejan,

I wouldn't worry about this. The MTU check never should have existed
in pseudowire signalling. It's even vendor dependent how they
calculate they MTU, so you might have exactly correct MTU in A-B end,
but you will get MTU mismatch because they calculate different thing
in A and B end.

I personally signal statically defined MTU, because that is more
transferrable, you may get B end which does not support ignore, but if
A end supports ignore + statically defined MTU, you can always get the
circuit up by just configuring A end correctly.

There is absolutely no impact to dataplane in signalling the MTU
correctly or incorrectly, it's just misguided attempt to avoid
configuration mistakes.

On 6 March 2018 at 10:17, Dejan Jaksic <dejan.jaksic at gmail.com> wrote:
> Hi all,
>
> we are testing interop for L2VPN VPLS BGP AD + signaling between Cisco
> ASR9k and Juniper MX.
> We cannot make pseudowire between Juniper and Cisco UP unless we ignore MTU
> mismatch, othervise during BGP signaling it states MTU mismatch error and
> PW stays down.
> When we use ignore mtu mismatch pseudowire goes up but under Cisco l2vpn it
> states 1500 bytes on Cisco and "unknown" on Juniper side.
> Looking at Juniper lsi interface under vpls connection for MTU it states
> "unlimited".
> Question - how to set up MTU for PWE on Juniper without ignore mtu to have
> VPLS PW up between Cisco and Juniper VPLS?
>
> Thanks,
> Dejan
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-- 
  ++ytti