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How to avoid DRs and neighbor command in OSPF

Core Issue

The functioning of the Open Shortest Path First (OSPF) protocol is dependant on the underlying topology. Based on the topology, networks can be broadly classified as broadcast multiaccess networks, nonbroadcast multiaccess networks, and point-to-point networks. The OSPF hello packets used to discover neighbors are  multicast packets. On Nonbroadcast Multiaccess (NBMA) networks, multicasts are not supported and this interferes with the process of OSPF neighbor discovery. For OSPF to function properly, the Designated Router (DR) and Backup DR (BDR) are required to be reachable from all other routers. This may not always be the case in a partially meshed network and makes it necessary to explicitly define neighbors and control DR and BDR election.

Resolution

To avoid explicitly defining neighbors and controlling DR and BDR election on NBMA networks, perform these options:

  • Use point-to-point subinterfaces.
  • Configure the OSPF network type as point-to-multipoint.
  • Configure the network type as broadcast.

For more information, refer to the Avoiding DRs and neighbor Command on NBMA section of OSPF Design Guide.

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Last update:
‎06-22-2009 03:32 PM
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