Subject: Re: gif(4) and gre(4) interact poorly with dynamic routing
To: None <>
From: Michael van Elst <>
List: tech-net
Date: 09/25/2004 19:11:05
carton@Ivy.NET (Miles Nordin) writes:

>The problem is, when one of these loopback aliases I've used for the
>tunnel outer destination becomes unreachable and then comes back, the
>tunnel stops working and then stays broken.  Here's a typescript from
>a gif tunnel that broke when I rebooted its endpoint.  gif seems to be
>the less quirky of gif and gre, in that I can get the tunnel working
>by changing the outer destination to a different address and change it
>back, on the endpoint that was not rebooted:

gif and gre cache the route to the destination when configured and
this cache isn't invalidated when the routing table changes.

There is no means to signal a routing table change, so my solution
was to expire and recalculate the route after some time. There is a
PR somewhere, but the GNATS query is down and I can't look it up :-)

                                Michael van Elst
                                "A potential Snark may lurk in every tree."