BGP Conditional Advertisement

[newnetman]

Hi All,

After very careful observation of BGP conditional route advertisement, i realized that Advertise-map, Exist-map and non-exist-map is as follows;

1.Advertise-map------Non exist-map

means when the non exist-map is not available advertise-map should be advertised.

2.Advertise-map ------ exist-map

meaning when the exist-map is available the advertise-map should also be advertised, and when the exist-map is not available the advertise-map should also not be advertised.

I am writing this out so that i could be corrected if i got it wrong.

3.Lastly and my main question for today; what is the purpose of inject-map?.

That seems a bit obscure from all the books i have read so far.....please help me,

preferably if you can use a very simple plain language like i used in numbers 1 and 2 above.

Thanking you all in advance.

[Jerry Ye]

Hi,

Just want to clarify advertise-map before explaining inject-map.

For advertise-map, the prefix in the advertise-map must exist in the BGP table first.

All routes that may be dynamically advertised or not advertised need to exist in the BGP routing table for conditional advertisement to occur.

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp3.html#wp1012658

However, inject-map works a little different, the prefix you want to inject to your neighbor doesn't have to be exist in the BGP table, only the parent prefix needs to be exist in the BGP table.

Like 10.0.0.0/8 is the parent prefix of 10.10.10.0/24.

A valid parent route must exist; Only prefixes that are equal to or more specific than the aggregate route (existing prefix) can be injected.

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp1.html#wp1013521

HTH,

jerry