BGP summry

Use a network statement to advertise the summary address

https://www.cisco.com/E-Learning/bulk/public/tac/cim/cib/using_cisco_ios_software/cmdrefs/auto-summary.htm

  1. Auto-summary: a router summaries its locally-originated BGP networks to their classful boundaries. Also, all reditributed subnets (into BGP, if a router has) will be summarized to their classful boundaries into BGP table.
  2. Synchronization: If your AS is a transit AS, synchronization prevents a BGP speaker from advertising a route to an EBGP peer until all routers within the speaker’s AS have learned about the route via an IGP.

https://networkengineering.stackexchange.com/questions/44563/bgp-no-auto-summary-and-no-synchronization-configuration