How to modify the BGP AS_PATH?

[emaillis]

Hi,

My router (Router C) is in a private AS.

A prefix that originated in a private AS goes to a second AS, which is a public one, before reaching my router.

Router A is the router that originates the prefix:

RouterA (AS A, private) ---> Router B (AS B, public) ---> Router C (AS C, private) --> ...

Router C needs to advertise this prefix but only with private AS C in the AS path. This can be done if, on router C, we configure a static route towards the prefix and we advertise it with the command "network" in BGP.

Meanwhile, in that case the prefix will be advertise even if it is no longer reachable.

Does anybody knows how to advertise this prefix dynamically with a modified AS PATH?

Thanks in advance,

Regards

Emmanuel MAILLIS

[ruwhite]

Router B could strip the private AS' off of the route from Router A as it advertises it to Router C.

http://www.cisco.com/en/US/tech/tk365/tk80/technologies_tech_note09186a0080093f27.shtml

Other than that, you could use conditional advertisement to make it so the route isn't advertised from C onward unless the path to B is up.

http://www.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_example09186a0080094309.shtml

:-)

Russ.W

[emaillis]

Thanks.

As you suggested, I decided to strip the private AS' off of the route from Router A as B advertises it to Router C. Then, I used the as override command to "convert" AS B into AS C.

Emmanuel