BGP network summary

When auto summary enabled:

  •  route advitised by network command, both summarized route and subnet route will be advitised
    1, network command without net mask will be regarded as classified network, summariezed network route will be generated and send to peer,will be matched when there is a subnet route entry in the routing table.
    2, network command with net mask will be matched when there is a subnet route entry in the routing table.
  •  route advertised by redistribute, only summarized route will be advitised. no subnet route entry.

When auto summary disabled:

  • network command with net mask configured need to be used to match route entry in routing table, matching will be precisely for both prefix and network. Only the route that precisely matchs the network command will be advertised
  • redistribute route will following the same rule as network command

Use aggregate command to manually generate a summary net route:

Aggregate command can be used to manually advertise a summary net, when there is ‘summary-only’ configured, then only the summarized net route will be advertised, not any subnet route. But in order to be able to generate aggregate-address, there must be at least one subnet route available in the routing table.

  aggregate-address xx.0.0.0 255.0.0.0 summary-only
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