Hi Klement,

> > an existing static NAT mapping that maps that IP address on the
> > inside to the same IP address on the outside.

> what is the point of such static mapping? What is the use case here?

We are using VPP for endpoint-independent NAT44. Then all traffic from
outside is normally translated by NAT dynamic sessions but we have
special treatment of traffic to a certain IP address that corresponds
to our BGP (Border Gateway Protocol) traffic, that should not be
translated, so then we have such a static mapping for that. If we do
not have this static mapping then VPP tries to translate our BGP
packets and then BGP does not work properly.

It may be possible to do things differently so that no such mapping
would be needed, but we have been using such a mapping until now and
things have worked fine apart from this infinite loop issue, that
happens when a client from inside happens to send something to our
special BGP IP address that is intended to be used from the outside.
That IP address is normally not used by traffic from clients, the
normal thing is for the router to communicate with the VPP server using
that address, from outside. This is why the out-of-memory problem has
appeared random and hard to reproduce earlier, it just happened when a
client behaved in an unusual way, that did not happen very often but
when it did, we got the out-of-memory crash and now we finally know
why. Now that we know, we can easily reproduce it, it is not really
random it just seemed that way.

Anyway, even if it would be unusual and possibly a bad idea to have
such a static mapping, do you agree that VPP should handle the
situation differently?

Best regards,
Elias

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