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By Administrator in All, Routing protocols

The purpose of stub areas in an OSPF network is to reduce the amount of routing information that routers within a single area have to manage. Essentially, this is achieved by the ABR of a stub area filtering all external advertisements and replacing them with a default route. In most cases, this could considerably affect the size of the routing table that must be maintained internally.

The following conditions need to be met for an area to be called stub:

  • The backbone area (area 0) cannot be stub.
  • No virtual links are allowed through a stub area.
  • No Autonomous System Border Routers (ABRs) are allowed in a stub area.
  • All routers in the stub area must be configured to treat the area as stub.

Stub areas could be very beneficial to an OSPF network but the network engineer should be well familiar with the network topology and traffic flow patterns before implementing them.

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