BGP Advertising a prefix

BGP will advertise a prefix if:

• the network command is used to specify the prefix to be advertised
• The prefix, with the exact subnet mask, exists within the routing table

OR

• The redistribute command is used to redistribute routes from another source, such as an IGP or a static route.

When using the auto-summary feature, the way the network command works is slightly modified.

Links:

https://networklessons.com/bgp/how-to-advertise-networks-in-bgp