Arista Switch BFD issue - custom port

[Jakub Nowacki]

On Tue, Aug 14, 2018 at 2:27 PM Ondrej Zajicek <santiago at crfreenet.org>
wrote:

> On Mon, Aug 13, 2018 at 03:14:10PM +0200, Jakub Nowacki wrote:
> > Hi,
> >
> > I'm running BIRD on Arista which allows access to Linux bash. I'm having
> > issue with running multihop BFD session on it and I believe it's related
> to
> > port being already binded.
> >
> > > bash-4.3# netstat -tulpen | grep 4784
> > >
> >  udp6       0      0 :::4784                 :::*
> > >       0          4269       -
>
> Hi
>
> I thing 4269 here is PID, what is the process? netcat should return the
> process name, which is not here, but perhaps it is some limited variant
> of netcat. Maybe BFD is implemented in control plane on Arista, so it
> collides on kernel level?
>

4269 is Inode, netstat for some reason doesn't show PID/process name for
ports related to BFD on Arista. This seems to be Arista thing not Bird, so
probably that's not a place to investigate this here.

Also, there should be an error message in the BIRD log related to bind
> errors.
>

I haven't seen any error messages in log, perhaps logging level were not
set for it. I'll double check it.


> > I couldn't find any configuration option for BFD to change port being
> used,
> > but maybe there is one?
>
> There is no such option. Perhaps we should add it, as BGP and RIP also
> have port option.
>

That would be super helpful. I could create Pull Request for it, but I've
only written in C++ years ago, never actually touched plain C, it can take
me some time.


> > Perhaps anyone run into similar issue and have a workaround?
>
> As a workaround you can recompile BIRD with changed BFD_MULTI_CTL_PORT in
> proto/bfd/bfd.h file.
>

That's what I did. After changing port to arbitrary value, which is not
taken on Arista it started to work. So it seems that BFD is failing due to
Arista OS.


> --
> Elen sila lumenn' omentielvo
>
> Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
> OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
> "To err is human -- to blame it on a computer is even more so."
>


-- 

Kuba Nowacki

Senior NetOps

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E: jnowacki at greywizard.com



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