Re: [mpls-linux-general] ipip and mpls

[James R. L. <jl...@mi...>]

Hello,

On Fri, Feb 16, 2001 at 10:15:37AM +0000, J=F6rn Seger wrote:
> Hi everybody,
>=20
> I'm not sure, this is an mpls-problem, but somebody might have had the
> same problem:
>=20
> imagine the following simple environmet:
>=20
> router1 --- ipip-tunnel --- router2 --- mpls-tunnel --- router3
>=20
> now I just want an IP-packet to be send from router1 to router3.
> The ipip-tunnel works fine and so do the mpls-tunnel. But when I work
> with the mentioned environment, the packets (pings) disappeare at route=
r
> 2.
> If I change one of the connection into a "normal route" everything work
> fine again.

Depending on the order of things the route cache maybe interfering.=20

Specifically the old route cache entry (using normal routing) may still b=
e
in use.  One thing to try to eliminate this, is to let the route cache
expire, or reboot router 2, then re-setup the MPLS tunnel, making sure no=
t
to send traffic from router1 to router3 before the MPLS tunnel is setup.
I will look thourgh the code this weekend to see if there if I am some ho=
w not
flushing the route cache at the right time.

Another thing to look for is RPF or spoof filters.  Debian and a couple o=
f
distributions put these in place, and hamper the use of MPLS tunnels (bec=
ause
they are by there nature uni-directional and are a-symetric, this
is exactly what RPF and spoof filters try to prevent :-).

One last thing to help us help you :-) is turn on MPLS debugging (mplsadm=
 -d)
and run a couple of pings, then turn it off (mplsadm -d again) and look a=
t the
kernel log (dmesg).  If the MPLS code is being triggered you'll see gobs =
of
debug messages, if the IP stack is the culprit you won't see any debug
messages.

I hope this helps,
Jim

> Could anyone tell me what to do to get this work?
>=20
> Thanks - J=F6rn
>=20
>=20
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--=20
James R. Leu