OSPF Routing loop?

[ashok_boin]

Hi,

Is there any possibility of routing loop occurence in OSPF network?

According to my idea, for Router and network LSA's, because of they don't change in transit, and with ADV Router field in those LSA's, OSPF prevents routing loops. What about the other LSA's?

Thanks in advance..

Regards..

Ashok.

[kkalaycioglu]

Contrast to distance vector protocols operating "routing by rumor" OSPF routers learns inf from the first hand. Every router announces only LSAa (say networks) connected to it and every router learns this info like you said. As long as link state databases of routers in a OSPF area are consistent there'll be no fear for loops.

Regards.

[ruwhite]

There are almost always transient loops during convergence in any network, using any routing protocol. The basic idea is, though, to reduce the length of those transient loops so they are meaningless. OSPF, IS-IS, EIGRP, and RIP are all designed so permanent routing loops will not be built within the network, and transient loops are minimized as much as possible.

It's not accurate to say that routing loops are more possible in a distance-vector protocol than in a link state--in fact, it might be the opposite in some networks, under some conditions. Remember that link state protocols require each router in the network to have a consistent database, and anything which prevents this from happening, or delays the propogation of information required to build a consistent database in all routers, can leave open gaps of time for the router's databases to be inconsistent, and thus form transient routing loops.

:-)

Russ.W