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OSPF and IS-IS Differences

•OSPF supports NBMA and point-to-multipoint links, IS-IS does not.

•IS-IS rides directly above layer two, versus on IP like OSPF, which may  offer a security advantage (IS-IS attacks cannot be routed).

•OSPF can support virtual links, IS-IS cannot (because it rides L2 directly).

•On broadcast networks, OSPF elects a DR and BDR which cannot be  preempted, whereas IS-IS elects only a single DIS which may be  preempted.

•OSPF designates a backbone area (area 0) for inter-area advertisements; IS-IS organizes the domain into two layers.

•OSPF routers can belong to multiple areas, IS-IS routers belong to exactly one area.

•OSPF has more strict requirements for forming neighbor adjacencies. The  hello and dead intervals must match, and the subnet mask must match  (except on point-to-point links).

Of course there any many more differences discussed in the paper, some  of which should be weighed carefully when deciding between an OSPF and  an IS-IS deployment.


Thanks friend

New Member

Welcome friend, You can go through the Blogs as well, That is excellent article for you

Thank you for the information provided. I will go through the document