As far as I understand:

EIGRP is a routing protocol and handles IP packets. IP packets are outfitted with the TTL field and thus, do not loop indefinitely like layer 2 frames do.

Why does EIGRP try to create a loop free topology?

2 Answers 2


All routing protocols try to avoid a loop topology. If there is a routing loop, data is not getting to the destination.

If the path from source to destination is A -> B -> C -> D, but there is a loop between B and C, data will never reach D.


The TTL field in the IP header does not eliminate a routing loop. It just prevents the packets from being endlessly caught circling in the loop once it exists in that after 255 hops at most, they will be dropped.

However, the routing loop is a state of routing tables on multiple routers where, for a destination, router A points to router B, router B points to router C, and so one, and finally, some router, say router X, points back to router A. The contents of the routing tables exist regardless of whether IP packets are flowing or not, and they are constructed using routing protocols. All routing protocols except EIGRP are prone to creating routing loops, even if short-lived. EIGRP is the only routing protocol guaranteed that it never, ever, creates a routing loop, even a transient one, if deployed correctly.

Best regards, Peter

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