OSPF loop prevention

OSPF is a routing protocol that, by design, has built-in loop prevention mechanisms to mitigate against routing loops.

First, as a link-state protocol, it enables each router to have a complete map of the network. This helps in preventing most routing loops.

Secondly, as OSPF networks get larger, they are separated into distinct areas. These areas are all obligated to connect to area 0, thus creating a loop-free inter-area topology where traffic from one area to another must go through area 0.

This whole design of OSPF helps to alleviate the possibility of having routing loops. There is no “loop avoidance” technique employed by OSPF since loop avoidance is built into the shortest path first (SPF) algorithm.

Routing loops may be introduced into OSPF whenever you interconnect with other routing domains running different routing protocols, especially if you have two or more connections to these other domains. In such cases, other techniques such as route tagging should be used to avoid routing loops.

Links:

https://forum.networklessons.com/t/redistribution-in-ospf/14671/4?u=lagapides

https://networklessons.com/cisco/ccie-routing-switching/how-to-configure-route-tagging