[j-nsp] ospfv3 - JUNOS sends zero mtu in dbd -> stuck in ExStart

[Volker D. Pallas]

Hi again,

yeah, this makes total sense!
At first I thought this is a JUNOS-problem, as Cisco does send the "right" mtu along.

I closed the bug report on the quagga bugzilla for now (with closed/invalid) and will
talk to JTAC.
I'll get back to you and the list as soon as I have some confirmation and/or fix.

 >I'm not so sure anymore. A fellow reader has challenged my
 >interpretation of the RFC wording, that it might mean "OSPF virtual
 >links", not tunnel (and similar virtual, non-physical) interfaces.
 >Upon re-reading with that interpretation in mind, I tend to agree.
 >
 >Thinking further about it, mtu=0 for OSPF virtual links makes sense, as
 >only OSPF PDUs are being tunnelled, no actual traffic. So there is no
 >sensible MTU to report in the DBD packets. On real tunneling interfaces
 >though, everything (OSPF PDUs and actual traffic) gets tunnelled, and
 >the tunnel has a real MTU associated.
 >
 >So in fact, I think my interpretation was wrong and JUNOS is actually
 >misbehaving by advertising MTU=0. It should report the tunnel interface
 >L3 MTU.
 >
 >Sorry for the noise. I suggest raising a case with JTAC and closing off
 >the Quagga bug filing.

No, not at all! Thanks a lot for your input! I did not even read the appropriate
RFC before you posted, which I should do next time.

 >BTW, I noticed your Linux tunnel interface being named "gre-nc" - I
 >guess the "gre" part is a leftover misnomer from trying GRE encaps?

exactly ;-) It's actually "sit" now on the linux side

 >Best regards from Porz to Porz,
 >Daniel

and best wishes back to you!

Volker