‘show ip eigrp topology all-link‘ command shows you all the possible routes to a particular destination network that is learned via EIGRP. The number after the slash sign is referred to as the ‘Reported Distance (RD)’ and corresponds to the best distance to the destination network.
RD is the neighbors distance to the destination network as reported in an EIGRP packet received from that neighbor.
The router learns about these routes by receiving EIGRP messages from neighbors that carry the routing information (Updates, Querys, Replys, SIA-Query, and SIA-Reply)
RD can also be referred to as the Advertised Distance….this is not the same as Administrative Distance.