[c-nsp] GRE tunnel problem

[Bruce Pinsky]

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Wolfgang Roth wrote:
> Dear Bruce,
> 
>> Your tunnel has no IP addresses assigned.  It therefore is unable to
>> forward IP packets.
>>
>> When the serial interfaces are down, how are you directing (routing)
>> traffic over the tunnels without any valid nexthops?
> 
> like this:
> 
> ip route 2.3.4.5 255.255.255.255 Tunnel0 10
> ip route 2.3.5.0 255.255.255.0 Tunnel0 10
> 


> If at least one serial link is up, OSPF is running between the routers.
> Static routes like the two above are configured for the fallback case
> (i.e. all serial links are down).
> 
> I thought assigning an IP address to tunnel endpoint is not mandatory
> and primary for monitoring purpose (or routing purpose like you wrote).
> Maybe this is my mistake here?
> 


Yes, sorta.  Take a look at your routing table.  You'll find that those
static routes don't even appear in the table. That's because without an IP
address, IP packets won't get forwarded/processed by the tunnel.  Only
after you add an IP address to the tunnel (or use IP unnumbered) is the
tunnel considered to be forwarding IP packets and the routes will be
installed in the table.

- --
=========
bep

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