Mailing List Archive: GRE Tunnel problems, slightly off-topic

GRE Tunnel problems, slightly off-topic

Aug 8, 2003, 2:35 AM

Post #1 of 3 (1361 views)

Hi folks,

I am extensively testing GRE compatibility between Linux (iptunnel
a.k.a. ip tunnel), FreeBSD (gre-tun) and OpenBSD (ifconfig gre0 tunnel
...). While the IP-IP stuff workes nicely so far and I consider my
configs correct and messed quite some time with sniffers
(self-confidence, I know :-)) Before flooding with configs I'd like to
request feedback on your GRE setups. Have you encountered any
incompatibility with Cisco encapsulation?

Question: When routing a prefix into a tunnel, would you rather use the
near or far end of the /30 link as gateway, "it depends" I guess? Linux
is capable of routing towards dev gre0, on the other OSs I guess one has
to rely on the attached pseudo-interface addresses.

Did you get any of the following combinations work:

OpenBSD <--> Cisco gre ip tunnel
Linux <--> FreeBSD

Linux --> Cisco only works in one direction (echo request, echo reply),
I have no clue why.

Muchas gracias,
Gernot

--
Dipl.-Ing. Gernot W. Schmied, MS Network Architecture & Operations
Senior Strategist Research Group
mailto:gernot.schmied@nanorg.org http://www.nanorg.org
PGP Fingerprint: 5D70 5690 47DA 9A21 D07E B9EE C764 C9B7 9B64 B27E

Re: GRE Tunnel problems, slightly off-topic [ In reply to ]

paul at clubi

Aug 9, 2003, 8:08 PM

Post #2 of 3 (1325 views)

Permalink

On Fri, 8 Aug 2003, Gernot W. Schmied wrote:

> Did you get any of the following combinations work:
>
> OpenBSD <--> Cisco gre ip tunnel
> Linux <--> FreeBSD
>
> Linux --> Cisco only works in one direction (echo request, echo reply),
> I have no clue why.

TTL of the tunnel perhaps?

check the ttl setting on the tunnel on both sides - linux defaults to
'inherit' carrier gre packet assumes TTL of the payload packet, iirc
- after that check the cisco very carefully.

> Muchas gracias,
> Gernot

regards,
--
Paul Jakma paul@clubi.ie paul@jakma.org Key ID: 64A2FF6A
warning: do not ever send email to spam@dishone.st
Fortune:
Innovation is hard to schedule.
-- Dan Fylstra

Re: GRE Tunnel problems, slightly off-topic [ In reply to ]

gernot.schmied at nanorg

Aug 10, 2003, 7:42 AM

Post #3 of 3 (1315 views)

Permalink

Paul Jakma wrote:
> On Fri, 8 Aug 2003, Gernot W. Schmied wrote:
>
>
> TTL of the tunnel perhaps?
>
> check the ttl setting on the tunnel on both sides - linux defaults to
> 'inherit' carrier gre packet assumes TTL of the payload packet, iirc
> - after that check the cisco very carefully.

Thank you all for the TTL suggestions. I'll report back with the results
of my investigation.

Best Regards,
Gernot

--
Dipl.-Ing. Gernot W. Schmied, MS Network Architecture & Operations
Senior Strategist Research Group
mailto:gernot.schmied@nanorg.org http://www.nanorg.org
PGP Fingerprint: 5D70 5690 47DA 9A21 D07E B9EE C764 C9B7 9B64 B27E