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Webcast-Catalyst9k
New Member

Default Route via two Tunnels

Is it possible to prevent recursive routing to a destination network:-

Example below:-

lab-yoc-g-2600-h#sh ip route rip

R* 0.0.0.0/0 [120/1] via 10.128.18.149, 00:00:01, Tunnel2

[120/1] via 10.128.18.145, 00:00:02, Tunnel1

lab-yoc-g-2600-h#traceroute 10.1.30.1

Type escape sequence to abort.

Tracing the route to 10.1.30.1

1 10.128.18.149 68 msec

10.128.18.145 68 msec

10.128.18.149 68 msec

Many thanks

Mark

6 REPLIES
Hall of Fame Super Gold

Re: Default Route via two Tunnels

Mark

There is probably some aspect of your question that I am not understanding. But the answer to the question that is posed is yes it is possible to prevent recursive routing to a destination network when there are 2 tunnels and a default route is learned through each tunnel. The important aspect of preventing recursive routing is that the route to the tunnel end point should not point through the tunnel.

HTH

Rick

Hall of Fame Super Gold

Re: Default Route via two Tunnels

Please explain the topology in full because if 10.128.18.149 has default static pointing back to .145 it's normal that you get routing loops (note, recursive routing is something else).

Hall of Fame Super Gold

Re: Default Route via two Tunnels

Whoops I misunderstood the topology then.

So unless your tunnel goes down due to recursive routing as Rick explained, it's normal that you see different hops in doing traceroute.

New Member

Re: Default Route via two Tunnels

Apologies I did mean routing loops and not recursive routing.

The topology in full although I am simulating this in a lab environment is we have a main site with two hub routers running HSRP between them each hub with an IPSEC/GRE tunnel to the spoke sites.

The default route is being advertised via the tunnels using RIPv2. The 10.128.18.x is the Tunnel interface addresses. So would it be normal to see the traceroute traverse both tunnels?

thanks

Mark

Hall of Fame Super Gold

Re: Default Route via two Tunnels

Mark

Yes it is normal behavior to see the traceroute traverse both tunnels. If any router has 2 equal cost routes to the same destination (which would be the case with a default route learned over each tunnel) then any traffic generated by that router will utilize both routes. It is normal to see 1 packet go over one tunnel and the next packet to go over the other tunnel. This is a normal outcome of the fact that packets generated by the router are process switched and process switching does packet by packet load balancing.

What you are seeing is normal behavior and is not a problem.

HTH

Rick

New Member

Re: Default Route via two Tunnels

Rick,

Thank you very much for your reply I really appreciate it.

Best regards,

Mark

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