BGP Advertise-map questions

[astanislaus]

I have a few questions pertaining to Conditional advertisements in BGP using advertise-map(s).

From the Cisco site the examples I have seen stipulate that the routes you redistribute into BGP are through the means of "network" statements.

The first question is, are you able to redistribute the route(s) you wish to control being advertised to neighboring BGP peers via an advertise-map through the "redistribute" command or must you use "network" statements?

The second question is, are you able to put a condition on more than one route that you may or may not want to advertise based on the condition you have set. In otherwords as an example I want to allow around 30 routes to be advertised towards a BGP peer if a certain route exists in the BGP routing table. For this I will obviously need to use an advertise-map with the exist-map statement. Is it possible to have this condition set on the 30 routes?

[jackyoung]

According to my understading. If the network is located in the router locally then you can use the network command to make it be included in the BGP routing table. Therefore, if there is no such network but you use the network command, it won'r appear in the BGP table.

If you use redistribution from other routing protocol, it is the same that only if the network is existing in the being redistributed routing protocol, then you can redistribute it into your BGP. However it does not require the network to be available locally, it only require it is learn from other routing protocol, once it is alive in the other routing protocol, then it can be redistributed into BGP.

For the second Q, yes, you can control what route can be advertised. You have to combine to use the route-map and advertise-map together.

Check below for more info. :

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

Hope this helps.

[astanislaus]

Regarding your answer to the second question - are you saying that this applies to only one route or can it be applied to many routes on the condition basis that you specify via exist map or non-exist map?

The link you pointed to doesn't clearly define this.

[jackyoung]

It can apply to many routes. The link which I stated is for the advertisement question. Please check below for the route-map in redistribution :

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008047915d.shtml

Hope this helps.

[astanislaus]

Jack Young,

Please see the attached:

[jackyoung]

Thanks for the capture.

Could you please provide the "sho ip bgp neighbors 192.168.15.1 advertised-routes" w/o shut down the FE 0 ?

For the result of shut down FE0 section, could you please advise what is the problem here ?

I found the router did not advertise the routes which is included in the route-map that due to the 96.96.96.0/24 does not exist.

Could you please also provide the result of "sho ip bgp neighbors 192.168.15.1" in both cases. I want to check the full output.

Moreover, what you described in the file that you want to make the router to advertise the routes of condition-routes if the watch route disappear. If this is the case, you should use "non-exist-map" in the peering command instead of "exist-map". Please try it and provide the result again.

Below for your reference.

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

Hope this help.