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New Member

BGP Conditional advertisement

Hi all, kindly refer to this document

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094309.shtml

now if i want this

If 192.168.50.0/24 exists in R102's BGP table, then do not advertise the 128.16.16.0/24 network to R101.

how can i accomplish this ? if i want to block advertisement of certain prefix when a particular prefix is in the BGP table then how can i do that ?

Thanks

7 REPLIES
Cisco Employee

Re: BGP Conditional advertisement

Ovais,

This is exactly what the example does, as per comments in the configuration example:

!--- Advertises the routes matched in the route-map ADVERTISE (128.16.16.0/24)

!--- only if the routes matched in route-map NON-EXIST (192.168.50.0/24)

!--- do not exist in the BGP table.

So if 192.168.50.0/24 is present, 128.16.16.0/24 will not be advertised.

If you wanted the opposite (i.e. advertise 128.16.16.0/24 only when 192.168.50.0/24 is present) then you would use an exist-map instead of a non-exist-map.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: BGP Conditional advertisement

Try this. I'm not at a router to test but see if it works for you.

access-list 60 permit 128.16.16.0 0.0.0.255

access-list 65 permit 192.168.50.0 0.0.0.255

route-map EXIST deny 10

match ip address 65

route-map ADVERTISE permit 10

match ip address 60

neighbor 10.10.10.1 advertise-map ADVERTISE exist-map EXIST

Again, try this in a test environment as I didn't have a chance to test this myself.

Cisco Employee

Re: BGP Conditional advertisement

Sparky,

This configuration would advertise 128.16.16.0/24 if 192.168.50.0/24 exists.

From the original poster:

"if i want to block advertisement of certain prefix when a particular prefix is in the BGP table:

Sounds like the opposite, right?

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: BGP Conditional advertisement

I guess, I was just giving ideas.

New Member

Re: BGP Conditional advertisement

hi guys, i got it done :) i was a bit confused but still did it, one thing for sure is that we cant use deny statements in any route-map ( advertise, exist and non-exist ) right ??

Cisco Employee

Re: BGP Conditional advertisement

Ovais,

That is correct. You need to work either with the exist-map or non-exist-map but the trigger has to be done on a permit.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Cisco Employee

Re: BGP Conditional advertisement

Sparky,

Understood. Thanks for your contribution to NetPro.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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