Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

GRE tunnel limit?

Hello,

Is there a limit on the number of GRE tunnels that can be configured on a router?

Any advice welcomed.

Thanks

Phil

Everyone's tags (1)
1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: GRE tunnel limit?

Phil

As Lei Tian points out there may be factors such as memory constraints that will place practical limits on how many tunnels you can support. But there is also a hard limit on the number of tunnels that you can configure. That limit is based on the limitation of the number of IDBs supported by your router. The IDB is the Interface Descriptor Block and each interface (physical, or tunnel, or loopback, or whatever) requires an IDB. The number of IDBs will vary by platform and sometimes by release level of the code that you are running. You can use the privileged command show idb to see what the limitation is on your router. On the 1841 router that I just checked the limit on IDB is 1200 (which is a pretty large number - I believe that you would encounter other limits on performance or on size of configuration before you exhaust the IDB limit).

HTH

Rick

3 REPLIES
Cisco Employee

Re: GRE tunnel limit?

Hi Phil,

I think that is a question depends on platform and IOS version. It is better to test it to find the answer, and you might hit resource limitation other than the number of tunnels, like cpu, memory.

HTH,

Lei Tian

Hall of Fame Super Gold

Re: GRE tunnel limit?

What prevents you from using multipoint GRE ?

Hall of Fame Super Silver

Re: GRE tunnel limit?

Phil

As Lei Tian points out there may be factors such as memory constraints that will place practical limits on how many tunnels you can support. But there is also a hard limit on the number of tunnels that you can configure. That limit is based on the limitation of the number of IDBs supported by your router. The IDB is the Interface Descriptor Block and each interface (physical, or tunnel, or loopback, or whatever) requires an IDB. The number of IDBs will vary by platform and sometimes by release level of the code that you are running. You can use the privileged command show idb to see what the limitation is on your router. On the 1841 router that I just checked the limit on IDB is 1200 (which is a pretty large number - I believe that you would encounter other limits on performance or on size of configuration before you exhaust the IDB limit).

HTH

Rick

1953
Views
0
Helpful
3
Replies