Recomended number of Area connected to ABR

[Ali Norouzi]

1- What's the best practice number of areas connected to ABR?

2- What's the nominal number of routers in each area?

[sean_evershed]

Hi, the answer to both questions depend on a number of factors. See below from the OSPF design guide:

http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t42

1- What's the best practice number of areas connected to ABR?

"The number of areas per ABR is a number that is  dependent on many factors, including type of area (normal, stub, NSSA),  ABR CPU power, number of routes per area, and number of external routes  per area. For this reason, a specific number of areas per ABR cannot be  recommended."

2- What's the nominal number of routers in each area?

I'm not sure what you mean by that however the guide states the following the maximum:

"The maximum number of routers per area depends on several factors, including the following:

• What kind of area do you have?

• What kind of CPU power do you have in that area?

• What kind of media?

• Will you be running OSPF in NBMA mode?

• Is your NBMA network meshed?

• Do you have a lot of external LSAs in the network?

• Are other areas well summarized?"

Please remember to rate all posts that are helpful.

[Langas Nicu-Daniel]

Hi,

I found these 2 questions on The Cisco Learning Network, ROUTE Set 6 Review Questions

4.	What is the recommended guideline for the maximum number of routers per OSPF area?
	50

8.	Cisco recommends no more than _____ area or areas per ABR in addition to area 0.
	one
	two

I hope this will be helpful for you.

Dan Langas