Cisco Systems GRE Tunnel

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Subject Author Date
GRE Tunnel tsvanduyn@yahoo.com 11-21-05
---> Re: GRE Tunnel neo80123@google...11-22-05
  ---> Re: GRE Tunnel tsvanduyn@yahoo...11-22-05
Posted by tsvanduyn@yahoo.com on November 21, 2005, 8:38 pm
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I have the following configuration on my router. Both router A and
router B show the tunnel 0 interface is up, line protocol is up. I can
ping 172.33.1.14 and 172.33.1.10 from both router A and router B. When
I try to ping 172.20.42.17 from router A the ping fails. I can ping
172.20.42.1 from router A (itself) without any problems. The same is
true for router B, I can ping 172.20.42.17 (itself), but not
172.20.42.1 the other end of the tunnel.

Does anyone know why the tunnel interface would say up and up but be
unable to ping the other side of the tunnel when I can ping both the
source and destination addresses of the tunnel endpoints? I can only
think that it would be a routing issue but, I'm not sure what I am
missing. Any help would be appreciated.

Router A

interface Tunnel0
ip address 172.20.42.1 255.255.255.224
ip pim sparse-dense-mode
tunnel source 172.33.1.14
tunnel destination 172.33.1.10

interface Serial0/1
ip address 172.33.1.14 255.255.255.252
ip pim sparse-dense-mode
no ip mroute-cache
load-interval 30
no fair-queue
no cdp enable

ip route 172.20.42.17 255.255.255.255 Serial0/1
ip route 172.33.1.10 255.255.255.255 Serial0/1

Router B

interface Tunnel0
ip address 172.20.42.17 255.255.255.224
ip pim sparse-dense-mode
tunnel source 172.33.1.10
tunnel destination 172.33.1.14

interface Serial0/0
ip address 172.33.1.10 255.255.255.252
ip pim sparse-dense-mode
no ip mroute-cache
load-interval 30
no fair-queue
no cdp enable

ip route 172.20.42.1 255.255.255.255 Serial0/0
ip route 172.33.1.14 255.255.255.255 Serial0/0


Thanks,
Travis


Posted by neo80123@googlemail.com on November 22, 2005, 8:49 am
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hi Travis,
As far as i know, connected Serial interfaces should be in the same
subnet to have direct connectivity. But u can try to set the routes
through the tunnel interface.

sth like that

ip route 172.33.1.14 255.255.255.255 172.20.42.1

regards,
sebastian


Posted by tsvanduyn@yahoo.com on November 22, 2005, 11:56 am
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Sebastian,

I guess I forgot to say that these two routers are connected through
MPLS cloud. They are not directly connected. I do have connectivity
because I can ping through the cloud but, I cannot use the tunnel
addresses to ping each other. Thank you for your response.

Also the route that you put in down there looks like it would cause the
endpoint of one of the the tunnel to go through the tunnel itself. I
thought that this was something that shouldn't be done. Doesn't this
cause some recurive routing errors?

Thanks,
Travis

neo80123@googlemail.com wrote:
> hi Travis,
> As far as i know, connected Serial interfaces should be in the same
> subnet to have direct connectivity. But u can try to set the routes
> through the tunnel interface.
>
> sth like that
>
> ip route 172.33.1.14 255.255.255.255 172.20.42.1
>
> regards,
> sebastian


Posted by Merv on November 22, 2005, 12:42 pm
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> Doesn't this cause some recurive routing errors?

YES


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