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New Member
Posts: 23
Registered: ‎06-09-2014
Kudos: 2
Solutions: 1
Accepted Solution

OSPF over GRE tunnel

I am not able to get two edgemax lite routers to set up an ospf neighbor relationship via GRE tunnel?

The two routers can see each other via the GRE tunnel but OSPF relationship will not form.

I can get the neighbor relationship to form If I put the two routers on the same lan segment. Once I put one hop in between them and a gre tunnel for the direct connection, the relationship fails to form.

Any ideas?

How do you debug ospf?


Accepted Solutions
New Member
Posts: 23
Registered: ‎06-09-2014
Kudos: 2
Solutions: 1

Re: OSPF over GRE tunnel

Issue Resolved:

I took a backup of the config with "show configuration commands".
Reset the device to factory defaults
Updated the firmware to the latest
Loaded the config back in via console.

The GRE tunnel came up right away, followed by the OSPF neighbor.

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Ubiquiti Employee
Posts: 2,991
Registered: ‎02-04-2013
Kudos: 354
Solutions: 289

Re: OSPF over GRE tunnel

ubnt@Etr# run show ip ospf 
Possible completions:
  <Enter>       Execute the current command
  border-routers
                Show IPv4 OSPF border-routers information
  database      Show IPv4 OSPF database information
  interface     Show IPv4 OSPF interface information
  neighbor      Show IPv4 OSPF neighbor information
  route         Show IPv4 OSPF route information

      
[edit]
ubnt@Etr# run debug ospf 
Possible completions:
  event         Enable OSPF event debugging
  ism           Enable OSPF ism debugging
  lsa           Enable OSPF lsa debugging
  nsm           Enable OSPF nsm debugging
  nssa          Enable OSPF nssa debugging
  packet        Enable OSPF packet debugging
  zebra         Enable OSPF zebra debugging

      

 If adjacency not established, first compare "show ip ospf interface" output from both routers. 

Veteran Member
Posts: 5,460
Registered: ‎03-12-2011
Kudos: 2749
Solutions: 129

Re: OSPF over GRE tunnel

Check for MTU issues. Firstly ensure you can ping across the tunnel, once done try a ping at the maximum MTU of the GRE tunnel, if it fails, that's probably your issue.

The ospf debug commands may assist too, along with show log.

New Member
Posts: 9
Registered: ‎06-12-2014

Re: OSPF over GRE tunnel

You should to check ttl value. By default quagga set ttl=1 for a packets and GRE used this. For GRE it must be more. test this via Linux console:

ip tunnel change gre1 ttl 64

Veteran Member
Posts: 5,460
Registered: ‎03-12-2011
Kudos: 2749
Solutions: 129

Re: OSPF over GRE tunnel


@a_s_y wrote:

You should to check ttl value. By default quagga set ttl=1 for a packets and GRE used this. For GRE it must be more. test this via Linux console:

ip tunnel change gre1 ttl 64


I have a gre tunnel on an EdgeMAX device and the ttl is set to 255 by default (ip tunnel show tunX), so at least on EdgeOS I can't see this being the issue. And if it was I'd expect more than OSPF to fail (ie, pings/etc).

New Member
Posts: 9
Registered: ‎06-12-2014

Re: OSPF over GRE tunnel

Good. :-)

I had this problem between JunOS and Linux some years ago:

https://lists.quagga.net/pipermail/quagga-users/2010-November/011960.html

New Member
Posts: 23
Registered: ‎06-09-2014
Kudos: 2
Solutions: 1

Re: OSPF over GRE tunnel

Issue Resolved:

I took a backup of the config with "show configuration commands".
Reset the device to factory defaults
Updated the firmware to the latest
Loaded the config back in via console.

The GRE tunnel came up right away, followed by the OSPF neighbor.

Emerging Member
Posts: 45
Registered: ‎07-05-2013
Kudos: 5

Re: OSPF over GRE tunnel

I had this issue recently although I was connecting between a cisco and edgemax. On the cisco I did a simple command that alleviated the issue I was having, which was basically that my ospf processes were stuck on EXSTART, which means it established the neighbor but cant get the routing table installed.

in the tunnel interface  on the cisco type:

ip ospf mtu-ignore

If someone knows the command to do this on a vyatta this would be helpful.

 this will ignore mtu requirements on the interface for ospf packets. Since GRE and IPSEC add lots of overhead to a packet you will usually get packets larger than 1500 bytes truncated and dropped. 

 

If you want a comprehensive guide to how MTU and GRE/IPSEC work together read this article, its a whopper.

 

http://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.ht...

 

 

Previous Employee
Posts: 13,551
Registered: ‎06-10-2011
Kudos: 5479
Solutions: 1656
Contributions: 2

Re: OSPF over GRE tunnel

Yeah that's under the interfac, e.g., "set interfaces ethernet eth0 ip ospf mtu-ignore" then commit etc.

Emerging Member
Posts: 45
Registered: ‎07-05-2013
Kudos: 5

Re: OSPF over GRE tunnel

thanks!