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OSPF and IS-IS: Choosing an IGP for Large-Scale Networks by Jeff Doyle

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8.4. Overloading

The previous section dealt with the issue of adjusting the size of LSAs and LSPs to existing link bandwidth—the assumption being that in large networks OSPF Updates and IS-IS can become very large. There is a “flip side” to this issue: What happens when a router’s memory is not large enough to store all of the LSA/LSPs being flooded in an area? We know that all link state databases in an area must be identical. If the memory allocated to storing the link state database becomes full so that not all information can be recorded, the SPF calculation at that router will likely be incorrect. The router then cannot be trusted to route correctly on the shortest-path tree and should not be included as a transit node.

IS-IS has a facility ...

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