why EIGRP AS ID is required while OSPF Process ID is not ?

[mohammed hashim]

hi,

when you want to establish an adjecency using these protocols EIGRP and OSPF,

in EIGRP when you configure router eigrp 100 , this AS ID should be identical on both routers,

but in OSPF, router ospf 100 , this is not required on other router, which means the other router can use something like router ospf 99

is there any technical reason behind this ?

[InayathUlla Sharieff · Accepted solution]

My understanding is that the EIGRP used the Autonomous system concept were in the group of routers running the eigrp should have the same AS number to form the adjacency and exchange there routing information. Using different AS means that network is under someone elses control or it was part of the design for some kind of policy.

Were in OSPF uses concept of areas were the process number is not the criteria to have the neighbour relationship. OSPF uses a process ID which is locally significant, it's not checked when forming adjacencies.

HTH

Regards

Inayath

[Milos Megis]

hi,
protocol is defined (and implemented) as you described. So it must be as you say.

[Mark Malone]

Hi

Its not best practice to have 2 ospf neighbours connected together with different process ids , unlike eigrp where the AS number is prerequisite for joining together its not in opsf its the way they were designed but that does not mean you should do it like that its not recommended , if you look at what is the required list for ospf to form you will see the process id is not 1 of them but in eigrp it is by design