[c-nsp] BGP route won't advertise

[Jerry Bacon]

I have the following layout:

Internet <--> R1 <--> R2 <--> R3 <--> R4 <--> Internet

I have a customer attached to R3 for whom I am doing transit.

R1, R2, & R4 are GSR 12008 running 12.0(32)S14
R3 is a 3825 running 12.3(11)T5

At R4 everything is fine:

R4#sh ip rou a.b.c.0
Routing entry for a.b.c.0/22, supernet
   Known via "bgp 1xx77", distance 200, metric 0
   Tag 11xx1, type internal
   Last update from x.y.z.242 1w5d ago
   Routing Descriptor Blocks:
   * x.y.z.242, from x.y.z.242, 1w5d ago
       Route metric is 0, traffic share count is 1
       AS Hops 1, BGP network version 0
       Route tag 11xx1

R4#sh ip bgp a.b.c.0/22
BGP routing table entry for a.b.c.0/22, version 40711009
Bestpath Modifiers: always-compare-med, deterministic-med
Paths: (1 available, best #1)
   Advertised to update-groups:
      5
   11xx1
     x.y.z.242 (metric 143104) from x.y.z.242 (x.y.z.242)
       Origin IGP, metric 0, localpref 100, valid, internal, best


However, at R1 the same route won't advertise:

R1#sh ip rou a.b.c.0
Routing entry for a.b.c.0/22, supernet
   Known via "bgp 1xx77", distance 200, metric 0
   Tag 11xx1, type internal
   Last update from x.y.z.242 16:03:41 ago
   Routing Descriptor Blocks:
   * x.y.z.242, from x.y.z.242, 16:03:41 ago
       Route metric is 0, traffic share count is 1
       AS Hops 1, BGP network version 0
       Route tag 11xx1

R1#sh ip bgp a.b.c.0/22
BGP routing table entry for a.b.c.0/22, version 406152
Bestpath Modifiers: always-compare-med, deterministic-med
Paths: (1 available, best #1)
   Not advertised to any peer
   11xx1
     x.y.z.242 (metric 143360) from x.y.z.242 (x.y.z.242)
       Origin IGP, metric 0, localpref 100, valid, internal, best

None of the issues that I have been able to find that might cause this 
behaviour seem to apply. Any ideas on what more to look for?

-- 
Jerry Bacon
Senior Network Engineer