Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

ospf area network types

Hi, I have been reading a little on ospf, what area types are there, ie NSSA, SA, etc, what does this mean to ospf, is there any config difference on the router and what benefit does it have ?

5 REPLIES

Re: ospf area network types

Hi,

1.Area concept of OSPF , is integrated as part of scalability & faster convergence feature of routing protocol.

2.As your network grows, the single change in network causes all routers to rerun the SPF algorithm & causing delay in convergence.

3.If you add more areas in the Network either geographically or logically , the SPF calculations are restricted to the area's & ABR area border routers advertise summary across area's resulting in faster convergence & high scalability.

4.Types of area's are

Backbone area Area 0

Stub Area

Totally Stubby

Not So Stubby

5.All these areas's are either some types of Link State Advertisements ( LSA ) & don't take other LSA, you need to decide which type of area you want as part of design

5.There is config differernce of few commands for every type of area.

6.Overall benefit is faster convergence & scalability

refer below links for more clarification

http://cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml

http://cisco.com/application/pdf/en/us/guest/tech/tk480/c1550/ccmigration_09186a0080187c6d.pdf

HTH..rate if helpful...

New Member

Re: ospf area network types

Hi there

Thanks for that

another question about ospf,

If my router has a link failure, does my router send an update to the DR, does thnis then send info out to all routers ?

with this information does every router have to re run the SPF alogorithm ?

Re: ospf area network types

Yes.

HTH>

New Member

Re: ospf area network types

what are they doing when running this algorithm? what are they looking to do? are they trying to find another route to the network? if so, shouldnt ospf already know about this other route?

Re: ospf area network types

OSPF uses Dijkstra's SPF algorithm to compute the shortest path tree (SPT). During the computation of the SPT, the shortest path to

each node is discovered. The topology tree is used to populate the routing table with routes to IP networks. When changes to a Type-1 or Type-2 link-state advertisement (LSA) occur in an area, the entire SPT is recomputed. In many cases, the entire SPT need not be recomputed because most of the tree remains unchanged.

Incremental SPF allows the system to recompute only the affected part of the tree. Recomputing only a portion of the tree rather than the entire tree results in faster OSPF convergence and saves CPU resources.

132
Views
5
Helpful
5
Replies
CreatePlease login to create content