[c-nsp] BGP route won't advertise

Jerry Bacon wireless at starbeam.com
Wed Feb 27 19:07:01 EST 2013

On 2/27/2013 3:47 PM, Jay Hennigan wrote:
> On 2/27/13 3:24 PM, Jerry Bacon wrote:
>> 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?
> No IGP route to x.y.z.242 from R1 and BGP synchronization enabled?
> Prefix-list or AS-path filter list on your EBGP neighbor on R1?
> Next hop of R3 not reachable from EBGP neighbor (need next-hop-self?)
> No-export community getting applied by a route-map?

I'm using EIGRP as my IGP, synchronization is disabled, and there is a 
good route to R3:

R1#sh ip rou x.y.z.242
Routing entry for x.y.z.242/32
   Known via "eigrp 100", distance 170, metric 143360, type external
   Redistributing via eigrp 100
   Last update from on GigabitEthernet2/0.283, 16:44:58 ago
   Routing Descriptor Blocks:
   *, from, 16:44:58 ago, via GigabitEthernet2/0.283
       Route metric is 143360, traffic share count is 1
       Total delay is 5020 microseconds, minimum bandwidth is 172413 Kbit
       Reliability 255/255, minimum MTU 1514 bytes
       Loading 23/255, Hops 2

I've tried with and without next-hop-self on R3, it doesn't seem to make 
any difference.

On R1, I have:

ip as-path access-list 16 permit ^$
ip as-path access-list 16 permit ^11xx1
ip as-path access-list 16 deny _11xx1_
ip as-path access-list 16 permit .*

On R4, I have:

ip as-path access-list 10 permit ^11xx1
ip as-path access-list 10 deny _11xx1_
ip as-path access-list 10 permit .*

I had to do this to keep from doing transit of other routes from this 

Jerry Bacon
Senior Network Engineer

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