With BGP, we must advertise the correct network and subnet mask in the "network" command ( in this case network 10.1.1.0/24 on R1 and network 10.2.2.0/24 on R2). BGP is very strict in the routing advertisements. In other words, BGP only advertises the network which exists exactly in the routing table. In this case, if you put the command "network x.x.0.0 mask 255.255.0.0" or
"network x.0.0.0 mask 255.0.0.0" or "network x.x.x.x mask 255.255.255.255" then BGP will not advertise anything.
It is easy to establish eBGP neighborship via the direct link. But let's see what are required when we want to establish eBGP neighborship via their loopback interfaces. We will need two commands:
+ The command "neighbor 10.1.1.1 ebgp-multihop 2" on R1 and "neighbor 10.2.2.2 ebgp- multihop 2" on R1. This command increases the TTL value to 2 so that BGP updates can reach the BGP neighbor which is two hops away.
+ A route to the neighbor loopback interface. For example: "ip route 10.2.2.0 255.255.255.0
192.168.10.2" on R1 and "ip route 10.1.1.0 255.255.255.0 192.168.10.1" on R2