Observe the diagram.

RTC is the hub router and RTA and RTB are the spokes. There are no virtual circuits between the
spoke locations. What is needed to successfully route traffic to the 11.11.11.0/24 network from
RTA?

A.
The neighbor 10.10.10.1 next-hop-self command on RTA.

B.
The neighbor 10.10.10.1 next-hop-self command on RTB.

C.
The neighbor 10.10.10.1 next-hop-self command on RTC.

D.
Nothing is required. This is the default behavior on this topology.

Explanation:
The following example illustrates the issue:
BGP Next Hop (NBMA)

If the common media as you see in the shaded area above is a frame relay or any NBMA cloud
then the exact behavior will occur as if we were connected via Ethernet. RTC will advertise
180.20.0.0 to RTA with a next hop of 170.10.20.3.
The problem is that RTA does not have a direct PVC to RTD, and cannot reach the next hop. In
this case routing will fail.
In order to remedy this situation a command called next-hop-self is created.
The next-hop-self Command
Because of certain situations with the next hop as we saw in the previous example, a command
called next-hop-self is created. The syntax is:
neighbor {ip-address|peer-group-name} next-hop-self
The next-hop-self command allows us to force BGP to use a specified IP address as the next hop
rather than letting the protocol choose the next hop.
In the previous example, the following configuration solves our problem:
RTC#
router bgp 300
neighbor 170.10.20.1 remote-as 100
neighbor 170.10.20.1 next-hop-self
RTC advertises 180.20.0.0 with a next hop = 170.10.20.2

http://www.cisco.com/warp/public/459/bgp-toc.html#bgpnexthop