Routing and tunnel problem

Gordon Chaffee (chaffee@CS.Berkeley.EDU)
Sun, 8 Feb 1998 12:11:40 -0800 (PST)


I'm trying to use the IPIP tunnel device in 2.1.8x, and I'm having some
trouble. Basically, it always tells me there is no route to the host.
This doesn't seem to be a problem in 2.0.3x.

Specifically, I'm trying to encapsulate the traffic for a single host
through a tunnel.

I create the tunnel and ifconfig it with

ifconfig tunl0 169.229.40.76 netmask 255.255.255.255

The trouble occurs when I try to route through tunl0:

route add -host gallia.cs.berkeley.edu gw 169.229.40.35 tunl0

This fails with a host unreachable error. I was able to workaround
the problem by setting the mask on tunl0 to be 255.255.255.0.
Then, I could do

route add -net 169.229.40.0 tunl0
route add -host gallia.cs.berkeley.edu gw 169.229.40.35 tunl0
route del -net 169.229.40.0 netmask 255.255.255.0
ifconfig tunl0 netmask 255.255.255.255

Since I should be able to route to an arbitrary destination through a
tunnel, it really shouldn't be checking if the destination is reachable
using the normal logic. It checks to see if there is a path from tunl0
to the destination host. This is incorrect because the packet passes
through tunl0 onto eth0 and uses eth0's routing table. I do have a
route from eth0 to 169.229.40.35.

- Gordon

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