I will try my best in describing as to where my confusion is. Kindly assist.
I have 4 Router's
Let's say, i have 192.168.4.0/24 on R2 from R3 through OSPF and in order to inject it in BGP. On R2 i have put a network statement " network 192.168.4.0 255.255.255.0. So in this way i get it injected into BGP the ospf route.
Okay now, what i am trying to do is I am planning to shut downt the R-3, and i will be received the same network from 192.168.4.0/24 from R1 to R2 through IBGP.
I cannot test the scenario in Lab, but in Production i have to make these changes, My argument is in order for 192.168.4.0/24 to work if i am learning from R1 through IBGP to R2 i have to remove the "NETWORK STATEMENT". Because i have got customers connected on R-2 (BGP-Connection) who would need 192.168.4.0/24. I simply receive this through IBGP from R1 and in Customer Route-maps i put this network and it will get advertised to them. Can someone kindly confirm if my assessment is right. If wrong, can someone guide me.
I thought it was this way.
From a practical point of view you can remove the network statement on R2 at any time because R2 is going to receive the prefix from R1.
Your migration steps could be:
a) remove network statement on R2's BGP
b) shut ospf link between R2 and R3
c) add a network statement for the prefix on R1
I just tried to clarify that once the prefix has been removed from the IP routing table of R2 that network statement under BGP plays no role anymore and R2 can accept the prefix from R1.
You are right when you state that you don't need the network statement on R2's BGP process in order to have the prefix sent out an eBGP session to the customer router. (this is part of BGP powerful charasteristics)
If you are not doing a migration but a new installation, you simply don't need the network command on R2.
hope to help