BGP prepend for certain network

[Krasnoperov]

Hi, I have an issue, I need to advertise for two ISP same network in bgp session. I have two routers with this config

ISP1(Router 1)

router bgp XXXXX

network 1.1.9.0 mask 255.255.252.0

network 1.1.11.0 mask 255.255.255.0

ISP2 (Router 2)

router bgp XXXXX

network 1.1.9.0 mask 255.255.252.0

network 1.1.12.0 mask 255.255.255.0

I do this, because more specific route (/24) in bgp is prefered, and I receive incoming traffic through certain ISP.

Now I want to advertise ONLY this common (for both ISPs) network 1.1.9.0 mask 255.255.252.0 with different as-prepends, how can I do this through route-map?

[JohnTylerPearce]

I would think you would do the following.

ip access-list standard 1

permit 1.1.9.0 255.255.252.0

route-map prepend permit 10

match ip address 1

set as-path

router bgp

neighbor x.x.x.x route-map prepend out

I would think that should send out that specific network range to the specific ISP BGP neighbor, with multiple same

AS PATHs, so it should choose the other ISP over this one.