We are still in the same LAB. What I want now to do is to change the hello interval. As this moment, the hello interval on both router is 10 seconds as we have checked in the previous LAB and that’s because we are in a broadcast network. Also, we know that in case the hello interval is not matched then the neighborship will not be formed anymore. I want to test this to see if really when changing the hello interval the neighborship will not be formed anymore.

Let’s change the hello interval on R1 to 11 seconds in place of 10 seconds.

I have changed the hello interval to 11 seconds on R1 while keeping the hello interval 10 seconds on R2. Then we have a mismatch.

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If the neighborship does not go down directly, do not panic. Remember, there is 40 seconds dead interval before the router consider the peer router not alive anymore.

Here I got a notification on R1 console that the neighbor is down:

Let’s now check what became the hello and dead interval on R1.

The hello interval is 11 seconds as we have set it, and the dead interval is 44 seconds, that means that by default the dead interval is 4 times more than the hello interval.

Finally, I need to check if R2 is not anymore shown as peer for R1 on OSPF.

Indeed, there is no peer with R1. This will prove to you that having a different hello/dead interval will affect the neighborship on OSPF.

I will fix again the problem in the background and make the OSPF neighborship to work again because this is needed for my upcoming LAB.

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