Absent Member.. JPhill Absent Member..
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NNMi 9.2 Cisco GRE Tunnels

Hello,

 

We are currently running NNM version 9.2 and have an issue with NNM discovering devices at the other end of a GRE tunnel.

 

We have a lot of remote sites connected via a variety of different carriers but all configured with a GRE tunnel back to the distribution router.

 

The problem we have is that most of the tunnels have been configured with "ip unnumbered Loopback10" instead of with a /30 link address. This means NNM is unable to discover the distribution router at the other end of the tunnel, and so does not understand how the remote sites connect into the rest of the network. Is there a way of configuring NNM to discover the device at the other end of the GRE tunnel without enabling CDP on the GRE tunnel and without re-configuring the tunnel?

 

This problem seems to only exist for sites where the GRE tunnels are configured to use the loopback as the GRE tunnel source, the sites where we have the tunnel configured with a /30 address are discvoered correctly.

 

I should also point out that NNMi is monitoring both ends of the tunnel.

 

Any help would be appreciated.

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2 Replies
Micro Focus Expert
Micro Focus Expert

Re: NNMi 9.2 Cisco GRE Tunnels

I am not quite sure what that command does

 

ip unnumbered Loopback10

 

and also physical connectivity diagram might have helped here but if NNMi cannot discover distributed router and the goal is to have it discovered, anyway then, I believe, the solution might be outside NNMi, for example: to add static route on NNMi server to the distribution router or setup another tunnel to connect them. This is networking task and I think not quite scalable solution in the end. Unforutenately, I see no other feasible option here since lack of OSI Layer 3, TCP/IP connectivity with the to be monitored nodes is quite an unbeatable condition.

Mikayel Grigoryan
HPE Software

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Absent Member.. JPhill Absent Member..
Absent Member..

Re: NNMi 9.2 Cisco GRE Tunnels

The Cisco command "ip unnumbered Loopback10"  uses the IP address that is assigned to the Loopback10 interface.

 

With the example I gave above with the GRE tunnel using "ip unnumbered Loopback10" the Tunnel is using the Loopback 10 address as it's source address.

 

So if you run a "show ip int brief" on the router you would see that the Tunnel interface and the Loopback10 interface have the same IP address. I think this is the reason why NNM is not monitoring the GRE interface because it sees it as a duplicate address.

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