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New Member

Problem Regarding GRE Tunnel

Dear Group,

I have been using a GRE tunnel for point to point connectivity with one of our remote site since long but now I am facing problem in this connectivity. The problem is that I am getting exactly 50% packet loss from remote end tunnel ip address while on the other hand tunnel destination addresses from respective routers are perfectly reachable without any packet loss. Kindly reply ASAP.

Regards,

Mujeeb Sarwar

7 REPLIES
New Member

Re: Problem Regarding GRE Tunnel

Hi,

It seems that some device wich does not let IP protocol 47 pass through was installed in the network and there is some kind of load balancing between 2 links used on the path.

//Mikhail Galiulin

Re: Problem Regarding GRE Tunnel

Hi

I do accept with Mikhail and feel more to do with 2 routes available for the remote network.

Do post out your config as well as the output of show ip route to your remote network.

Also you yourself can view the show ip route and troubleshoot the parallel path in addition to the primary path which is dropping the packets..

regds

Hall of Fame Super Silver

Re: Problem Regarding GRE Tunnel

When I hear about a problem like this that exhibits 50% packet loss my first reaction is to suspect that some device has two routes to the destination but that only one of the routes reaches the destination and the second route drops packets.

Perhaps the original poster can supply some additional information about the topology. Is it multiple remote routers to a single hub site or is it multiple peer to peer connections? Is the 50% packet loss on several tunnels or is it on a single tunnel?

I am not clear whether the 50% packet loss is in both directions or is in a single direction?

The output of traceroute to an address where there is packet loss might also help.

If the original poster can clarify this it might help us find a solution.

HTH

Rick

New Member

Re: Problem Regarding GRE Tunnel

Dear Rick,

The tunnel destination is reachable from Internet via our upstream ISP. 50% packet loss is in both direction and only in that specific tunnel. Tunnels with other destinations are working fine.

Regards,

Mujeeb

Hall of Fame Super Silver

Re: Problem Regarding GRE Tunnel

Mujeeb

If it happens on a single tunnel and it happens in both directions I hope that makes it easier to troubleshoot.

If you could provide some more details, we can help to solve it. could you post the configuration of the tunnel from both routers? Also it would help if you post the show ip route for the destination that you are attempting to access and a show ip route for the tunnel end point. And as I suggested the output of a traceroute might be helpful.

HTH

Rick

New Member

Re: Problem Regarding GRE Tunnel

Dear Rick,

For Example:

RouterA

interface Tunnel0

ip address 10.50.50.34 255.255.255.252

tunnel source 192.168.1.1

tunnel destination 172.16.2.2

I can ping 172.16.2.2 with source 192.168.1.1 ( no packet loss )

and also from other end I can ping 192.168.1.1 with source 172.16.2.2 ( no packet loss )

One more thing which I want to share is, I took a extended ping with record option of remote end tunnel ip address which was 100 % success rate.

Reply to request 4 (76 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(10.50.50.34)

(10.50.50.33)

(10.50.50.33)

(10.50.50.34)<*>

(0.0.0.0)

(0.0.0.0)

(0.0.0.0)

(0.0.0.0)

(0.0.0.0)

End of list

Success rate is 100 percent (5/5), round-trip min/avg/max = 36/56/76 ms

Regards,

Mujeeb

Hall of Fame Super Silver

Re: Problem Regarding GRE Tunnel

Mujeeb

This is helpful information and seems to show that the tunnel is reliable and there is no packet loss in the tunnel itself.

I thought I understood in the original post that you experience packet loss in ping to the other end of the tunnel. This seems to show no packet loss to the end of the tunnel. Perhaps you can help me understand what the problem is?

If you would post the output of show ip route and the output of a traceroute to the destination address it would help identify the problem.

HTH

Rick

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