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New Member

Conditional Advertising under BGP

Hi, all

Given: Networks A, B, and C are learned via an IGP.

Goal: I want BGP to summarize A, B, and C as D, and advertise D to its peers.

Restriction: BGP is to only advertise D if A, B, and C are all present in the routing table. If any one of A, B, or C is missing, BGP should not advertise D. For example, if C is not present, but A and B are, BGP should not advertise D.

I will use the aggregate address command to create D.

However, I am unsure how to create the condition that makes BGP ensure that A, B, and C are present before it advertises D. I am currently researching the advertise map, but I don't know if that will do it.

Does anyone have any pointers or suggestions, or can confirm I am heading in the right direction?

Thank you,


New Member

Re: Conditional Advertising under BGP

just an idea never tried it before :

When U recieve or originate route for netw A add the

community say 100 .

Say 200 for Netw B , say 300 for NETW C .

Agregate with As-set .

Filter out based on the existance of agregate

address and the commuintie list 100 200 300 .

Say the agregate is

Nei XXXX route-map mymap permit 10

match ip address 1

match community-list 2

access-list 100 permit host

ip comm-list 2 permit 100 200 300

if any route from A or B or C is missing the agregate

will not have it's community .


New Member

Re: Conditional Advertising under BGP

Well, that may or may not work for those routes already learned via BGP. I am referring to those routes learned via IGP that are to be advertised via BGP using the aggregate-address command.

In other words, BGP will have to make decisions based on routes in the IGP, not on the routes in BGP.



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