[c-nsp] GRE Tunnels and vrfs

[Gert Doering]

Hi,

On Sat, Sep 11, 2004 at 09:33:29AM +0300, Mihai CHELARU wrote:
> I wanted to setup some tunnels and put them into a vrf. Configuration 
> looks like this:
> 
> 
> int tun0
> tunnel source 192.168.0.1
> tunnel destination 192.168.2.1
> ip vrf forwarding test
> ip add 10.0.0.1 255.255.255.252
> 
> This is on a 2611XM.
> Now, the problem is that this setup is not working but in certain 
> conditions I'll describe latter.
> 
> Question 1: do tunnel src and dst need to belong to the test vrf ?

No.  (Of course not - this is usually done to connect VRF islands
over non-MPLS networks)

> Question 2: Why is this setup working after I disable CEF ?

How exactly is this "not working" with CEF?

There are lots of funny bugs in GRE tunneling with CEF regarding TTL 
decrementation (TTL not being decrement -> router not visible in 
traceroute, and worse, if you have a loop, the packet will loop forever, 
burning CPU like mad).

> Question 3: How can I solve it without 'tunnel vrf' that exists in only 
> in 12.3T ?

What you have should work fine.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de