Default delay value on tunnel interfaces - differing values on different IOS?

[chris.young]

I have come upon something and was looking for some clarification.

I am seeing default delay values for tunnels on different IOS as being different.

I haven't gone through all of the different IOS verson on all routers yet - but it appears that routers with 12.4T version of IOS will have a default delay value of 50,000 usec on a tunnel interface. It also appears that IOS of any other version will have a default value of 500,000 usec. So far I have been unable to find any documentation on this discrepancy.

This is a problem as this affects route paths between remote sites. This will also be difficult to remedy as I will have to either upgrade IOS and/or change default delay values on many many routers.

Can anyone provide any insight into these default dealy values for tunnels and if in fact it is related to IOS version.

Thank You.

[Laurent Aubert · Accepted solution]

Hi Chris,

What you see is correct. The default values of bandwidth and delay have been change in 2007 (CSCse69736) for the following reason:

- Increase scalability and stability of EIGRP in DMVPN deployment. EIGRP will use the bandwidth parameters to fix the maximum bandwidth it can use for its own needs. With a previous default value of 9kbps, it may not have enough Bw when the number of spoke increases and you will see session flapping.

My recommandation is to define the right value for those two parameters (you can use the new default one) and configure them explicitly everywhere to be consistant.

HTH

Laurent.

[chris.young]

That clarifies what I was seeing.  Thank you!

Chris