LARTC - May 2002 - gre tunnel question again

This question adds on to the GRE tunnel query that I
asked earlier.

For the GRE tunnel to work, do I need to configure
tunnels in both directions.

When I configure a tunnel in one direction, I get this
error :

protocol 47 unreachable which is an icmp error
message.

Can I configure a tunnel in one direction, and add a
static route in the other direction and expect it to
work?

Thanks,
Vikas



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On Thu, 16 May 2002, Vikas B. Wadhwani wrote:
> This question adds on to the GRE tunnel query that I
> asked earlier.
>
> For the GRE tunnel to work, do I need to configure
> tunnels in both directions.
You need to configure the tunnel on both endpoints, as both
endpoints have to cooperate to provide the tunnel.

So, if you have machine A with IP address 172.16.8.1 and machine B with IP
address 172.16.16.1 then you would for example use

 ip tunnel add abtun mode gre remote 172.16.16.1 local 172.16.8.1
 ip addr add 192.168.0.1 peer 192.168.0.2 dev abtun
 ip link set abtun up

on machine A and

 ip tunnel add abtun mode gre remote 172.16.8.1 local 172.16.16.1
 ip addr add 192.168.0.2 peer 192.168.0.1 dev abtun
 ip link set abtun up

on machine B to get the tunnel up and running. Then you should be able to
ping the endpoints on the other side, if the GRE encapsulated packets are
not being firewalled somewhere along the way.

Note that routing is at another level in the protocol stack.

Doei, Arthur.

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