03-07-2012 05:10 AM - edited 03-04-2019 03:34 PM
Hi,
I want to announce an iBGP learned route to eBGP peers..
this is my output
R8#sh ip bgp neighbors 203.172.5.1 advertised-routes ; this is my eBGP neighbor
BGP table version is 14, local router ID is 180.20.61.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 200.141.227.0/24 180.31.0.3 0 32768 i
*> 200.141.228.0/24 180.31.0.3 0 32768 i
*> 203.172.21.0 180.31.0.3 0 32768 i
Total number of prefixes 3
R8#sh ip bgp sum
BGP router identifier 180.20.61.1, local AS number 54444
BGP table version is 14, main routing table version 14
11 network entries using 1287 bytes of memory
11 path entries using 572 bytes of memory
4/3 BGP path/bestpath attribute entries using 496 bytes of memory
2 BGP AS-PATH entries using 48 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 2403 total bytes of memory
BGP activity 395/384 prefixes, 405/394 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
180.20.5.1 4 54444 16748 16974 14 0 0 6d20h 1
200.211.241.253 4 28103 263600 263594 14 0 0 1w6d 1
85.200.47.189 4 23201 301740 279483 14 0 0 06:13:21 0
203.172.5.1 4 27768 361491 361704 14 0 0 2d07h 0
R8#sh ip bgp 179.35.3.0
BGP routing table entry for 179.35.3.0/24, version 14
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
23456
200.141.226.42 from 180.20.5.1 (180.20.5.1)
Origin IGP, metric 0, localpref 100, valid, internal, best ; This is the ibgp learned route not advertised to my ebgp peers
R8#sh ip protocols | begin bgp
Routing Protocol is "bgp 54444"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
IGP synchronization is disabled
Automatic route summarization is disabled
Neighbor(s):
Address FiltIn FiltOut DistIn DistOut Weight RouteMap
180.20.5.1
200.211.241.253
85.200.47.189
203.172.5.1
Maximum path: 1
Routing Information Sources:
Gateway Distance Last Update
200.211.241.253 20 1w6d
180.20.5.1 200 6d20h
Distance: external 20 internal 200 local 200
according to this:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800945ff.shtml
in the part "Unable to Announce iBGP-Learned Routes"
they give the solution, disabling IGP synchronization... but in my case, IGP is already disabled.. how can I solve this?
greetings
Solved! Go to Solution.
03-07-2012 09:37 AM
Miguel,
You've told use that there is no filtering. However, your config shows that towards 201.217.5.1, you are using the prefix-list prov3 to filter out advertised updates. Would you mind posting that prefix list here - or at least review it to see if the network 200.124.120.0/24 is permitted by it?
Best regards,
Peter
03-07-2012 06:42 AM
Hi,
as AS number 23456 is used as AS_TRANS for 4-octet AS peering
(see http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6599/white_paper_c11-516826.html )
your problem might be related to that somehow?
BR,
Milan
03-07-2012 07:01 AM
hi, I don't think that should be related (the ASN of the not-advertised route is the version of 4 bytes), as far as I understand, the issue with 4 bytes ASN is related just with the peering of BGP neighbors (we've done that already, successfully). The criteria of advertisment of a route via BGP is not based on the ASN, is based in others parameters and configurations... and those parameters and configurations, to make this iBGP learned route to be advertised to a eBGP neighbor, are the ones which i'm not finding and are driving me crazy :S
regards
03-07-2012 07:21 AM
Hi,
without knowing more details, only trivial hints coming to my mind, like:
1) any route-maps/filter-lists used on R8 to filter prefixes advertised?
2) is the 190.114.226.42 next-hop reachable from R8? If not, wouldn't nei ... next-hop-self used fo iBGP peering help?
BR,
Milan
03-07-2012 07:43 AM
Milan, in the last post, I've outlined the topology of my situation, does it help?
Answering your questions:
1) no filters are implemented,
2) is not a next hop reachable from R8
03-07-2012 06:52 AM
Hi Miguel,
can you provide us a picture of your topology? This would give us a mucher better understanding of the whole setup/problem.
regards,
Dirk
BTW: Please rate if helpful
03-07-2012 07:18 AM
Yes, it is like this:
(200.124.120.0, ASN X, 4 bytes format)-->Router_A<---eBGP--->Router_B<-----iBGP--->Router_C<---eBGP--->Router_D
Router A and Router B are eBGP peers, differents ASs.
Router B and Router C are iBGP peers, same AS
Router C and D are eBGP peers, different AS
Router A and D are not in my control
Router B and C are in my control
Router C has the config I've posted in the first post
Router C learns from Router B the route to 200.124.120.0, via iBGP, and can fully route until there
I want Router C to advertise this route, learned via iBGP, to its eBGP peers, but this route is not advertised to any peers (as it's shown in the config)
IGP is disabled, and this is the solution that accross the internet is proposed for cases like these, but doesn't work for me
thanks people for the interest,
regards
03-07-2012 07:40 AM
Hi,
have you already tried clear ip bgp * out and if not do it and if it doesn't work post the result of debug ip bgp update.
Regards.
Alain
03-07-2012 09:21 AM
didn't work the clear ip bgp :s
the output:
Router_C#clear ip bgp * out
Router_C#sh ip bgp 179.35.3.0
BGP routing table entry for 179.35.3.0/24, version 14
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
23456
200.141.226.42 from 180.20.5.1 (180.20.5.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
Router_C
#debug ip bgp
Router_C
#debug ip bgp u
Router_C
#debug ip bgp updates
Mobile router debugging is on for address family: IPv4 Unicast
Router_C#
03-07-2012 09:17 AM
Miguel,
This is indeed a very interesting issue. In addition to the debugs asked for by Alain, do you believe you could also post the BGP configuration from the router C, i.e. show run | section router bgp ? Even if it appears plain and common, there may be something worth looking at.
Best regards,
Peter
03-07-2012 09:28 AM
Peter,
The config i've posted is from Router C, here is what you asked
Core_Borde#show run | section router bgp
router bgp 54444
no synchronization
bgp log-neighbor-changes
network 200.141.224.0 mask 255.255.248.0
network 200.141.224.0 mask 255.255.255.0
network 200.141.225.0 mask 255.255.255.0
network 200.141.226.0 mask 255.255.255.0
network 200.141.227.0 mask 255.255.255.0
network 200.141.228.0 mask 255.255.255.0
network 200.141.229.0 mask 255.255.255.0
network 200.141.230.0 mask 255.255.255.0
network 200.141.231.0 mask 255.255.255.0
network 200.124.120.0
network 203.172.21.0
neighbor 180.20.5.1 remote-as 54444
neighbor 180.20.5.1 update-source Loopback0
neighbor 200.211.241.253 remote-as 28103
neighbor 200.211.241.253 prefix-list prov1 out
neighbor 85.200.47.189 remote-as 23201
neighbor 85.200.47.189 prefix-list prov2 out
neighbor 203.172.5.1 remote-as 27768
neighbor 203.172.5.1 prefix-list prov3 out
no auto-summary
the bolded one is my iBGP neighbor from which I am receiving the updates
Regards
El mensaje fue editado por: Miguel Gonzalez
03-07-2012 09:37 AM
Miguel,
You've told use that there is no filtering. However, your config shows that towards 201.217.5.1, you are using the prefix-list prov3 to filter out advertised updates. Would you mind posting that prefix list here - or at least review it to see if the network 200.124.120.0/24 is permitted by it?
Best regards,
Peter
03-07-2012 01:12 PM
the problem was in the prefix list!
I'm not enough trained in bgp... thanks a lot! it is working now.
I've permited my previously non-advertised, iBGP learned route, in each prefix list for each eBGP neighbor, and after that i've "clear ip bgp * out"... then the route started to be advertised to the peers
03-07-2012 10:50 PM
Hi Miguel,
We were glad to help. Please note that it was Milan's first set of questions that mentioned the filtering as the possible reason for your problems, so he deserves to be credited with the correct answer as well. Also, in future, please post the configurations along with your description of the problem. Often, the problem really lies in overlooking or misinterpreting a part of the existing configuration.
Best regards,
Peter
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