Question about OSPF flat network design

[Yuyang Jin]

Hi all,

I have a question for OSPF flat network design. From the old time material, it is said that it is wise to put no more than 50 nodes in single area. Does it still suit to the current enviroment when powerful router like ASR9000, CRS, GSR are deployed? considering they are based on IOS XR platform with high-performance processor and memory.

Would it be big issue nowadays if there are around 100 nodes with around 150 links to be put in OSPF flat network?  

Thanks 

[Reza Sharifi]

Hi,

It is more a convergence issue than a router being able to handle the amount of nodes/routers.

In many OSPF area designs, the question of the  optimal size of the area (number of nodes and links) is often a primary  consideration in specifying the OSPF area boundaries, but does not play  as key a role in the campus as it can in a general design. The desire to  map the area boundaries to the hierarchical physical design, enforce  hierarchical traffic patterns, minimize the convergence times, and  maximize the stability of the network are more significant factors in  designing the OSPF campus than is optimizing the number of nodes in the  area or the number of areas in the network.

Also see figure-13 in this link:

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/routed-ex.html

HTH

[svibeesh85]

Mate, the routers have indeed grown powerful, but so has the size of the network & the no of routes in the table.

So in a practical perspective convergence time would be the key factor.