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OSPF

rachelhor
Level 1
Level 1

Hi,

Can some1 reply to my queries?

Q1) what is the max number of routers running OSPF in Area 0 before we need to split the network into different Areas? If no benchmark is available, based on your experience

Q2) What is the best optimised value that we can tune the OSPF to?

What are the issues or impact with tuning the OSPF to the lowest values available? Overheads? Bandwidth? Unstable routes?

Q3) When tuning OSPF, do we tune based according to how many routers there are in the network? Or we tune to the optimised value and used these values for network regardless of how many routers there are?

Tks!

3 Replies 3

Joseph W. Doherty
Hall of Fame
Hall of Fame

See if the section OSPF Internetwork Design Guidelines within http://www.cisco.com/en/US/tech/tk1330/technologies_design_guide_chapter09186a008075ac71.html#wp3548 helps.

For OSPF, can we have 2 separate Area 0 and interconnected via FE or WAN links?

Also, what are the issues with tuned OSPF for very large network?

"For OSPF, can we have 2 separate Area 0 and interconnected via FE or WAN links?"

You never want to have more than one Area 0, and connections can be via any type of link.

"Also, what are the issues with tuned OSPF for very large network?"

Depends what you mean by "tuned". The most common tuning option is adjusting neighbor timers. This can impact, especially on shared broadcast media, whether OSPF believes it loss a path, when it hasn't, or be slow to detect such loss.

Large networks, those with a large area topology, are more likely to overload routers when the topology changes, due to the SPF calculation.

Area design is very critical along with area types and address summarizations for large OSPF networks. I think of this as design, not tuning.

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