Router Server problem

[pramod babu G]

hai all,
  I am simulating an IXP and this has 4 router servers which are connected 
to the ISP routers.
I connected the 4 router server by means of Internal Bgp. This is as shown 
below
		IBGP
ISP1------ RS1------- RS2 ------ ISP3
         |               |
ISP2------                --------ISP4

Now the routes injected by ISP1 into R1 are received by ISP2. And there is 
exchange of routes between ISP3 and 4. But the routes send by ISP3 are not 
seen by ISP1 and ISP2. But RS1 has got those routes in its data base. 
These routes are not selected as best routes in the RS1 bgpd

So to overcome this do u have any suggestions ??