Hi Abhinay,
Are you practicing for a lab or general knowledge growth?
SIA is like playing detective. Someone is not replying to a query and you have to find out two things:
1) Find out where/who isn't responding
2) Find out why it's not respodning
Regarding the first point, you can use the "show ip eigrp top act" to start. There may be multiple routes SIA but just start with one prefix and look for it's neighbor that has the little r which means we're waiting on a reply. Then you login into that neigbor and follow the trail.
The reason why we aren't replying can range wildly. High cpu, bandwidth congestion, etc.
I've seen cases where their routing was messed up and they had congestion and a ton of output drops which in turn caused the box to not respond.
This guide talks about SIA too:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008010f016.shtml
In DMVPN scenario we see lots of customer's not use EIGRP stub on their spokes. This is probably the number one thing to ensure you have in your DMVPN setup.
-JY
