BGP network command

[lkadlik]

If I enter the following two network commands:

network 172.20.0.0

network 172.16.3.0

Will BGP pick up that the 172.20.0.0 network is a /16 and that the 172.16.3.0 is a /24 or do i need to use the mask portion of this command?

Thanks

[milan.kulik]

Hi,

BGP network command is expecting a classful network used.

network 172.20.0.0

is OK, as 172.20.0.0 is a class-B network.

For a classless prefix, you need to use

network 172.16.3.0 mask 255.255.255.0

command form.

IMHO,

network 172.16.3.0

is treated as a configuration error - surprisingly does not bring any error message/warning unlike "network 172.16.3.0 mask 255.255.0.0" does.

HTH,

Milan

[francisco_1 · Accepted solution]

The behavior of the network command varies depending on whether auto-summary is enabled or disabled. When auto-summary is enabled, it summarizes the locally originated BGP networks (network x.x.x.x) to their classful boundaries (auto-summary is enabled by default in BGP).

When auto-summary is disabled, the routes introduced locally into the BGP table are not summarized to their classful boundaries.

Francisco.

See this http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800945ff.shtml

Francisco