Today a little review :

edge12.bor03>show ip bg 37.8.8.8
BGP routing table entry for 37.8.0.0/20, version 47221703
Paths: (3 available, best #2, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  15975, (received-only)
    17.69.240.117 from 17.69.240.117 (17.69.255.1)
      Origin IGP, metric 16, localpref 500, valid, internal
  12671 15975 15975 15975 15975, (received & used)
    46.218.1.1 from 46.218.1.1 (172.17.1.6)
      Origin IGP, localpref 100, valid, external, best
  12671 15975 15975 15975 15975, (received & used)
    46.218.1.1 from 46.218.1.1 (172.17.1.2)
      Origin IGP, localpref 100, valid, external
edge12.bor03>

Why the path through 17.69.240.117 is not used, although it is the a better path to 37.8.0.0/20 ?
Why is it marked as “received-only”

“Received-only” means as it says that this prefix is received, stored in Adj-IN, but cannot be selected for a valid prefix. Why ?

Lot of reasons. Commons are : route-maps, NEXTHOP not reachable…

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html

In my example, the problem is here : a route-map without an explicit permit.