....why only Eigrp seems to be immune to microloops?....
Hi PGallo, Good to hear from you.
I don't think EIGRP is completely immune, but it is engineered to be faster than other routing protocols.
What does EIGRP do that the other protocols don't do (out-of-the-box
with no modifications)? It attempts to recognize a Feasible Successor for each prefix, in case it is needed, without recalculating everything.
WHITE wrote a blog about this a few years ago. The last paragraph of
his blog hints at a couple of the solutions that go further than even
EIGRP does. (fast-reroute and Ordered-FIB) EIGRP still has to look up and install the Feasible Successor, right?
But with Fast-Reroute, the repair route is already installed and ready
to go -- giving it a headstart on normal routing protocol methods.
Microloop! - blog by Russ White
Four Steps to Fast Convergence -- Russ White
1. Discover Failure - How long?
2. Report - How long to spread the news?
3. Calculate - How long for new path? <-- Eigrp tries to do this beforehand.
4. Install - how long for change to new path? <-- EIGRP still must install.