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Question regarding BGP 'Routing Information Sources'

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George Joseph
Level 1
Level 1

‎02-08-2015 05:27 PM - edited ‎03-05-2019 12:45 AM

Hello Team,

 

I've got few questions regarding the BGP 'Routing Information Sources' section under the bgp portion of 'show ip protocols'.

 

1) Why not all the bgp neighbors listed under 'Routing Information Sources'?

 

2) Are  we supposed to see only configured neighbors under that section or other g/w ips as well?

 

3) What is that field for (actually)?

 

 

R1#sh ip bgp sum     
BGP router identifier 192.168.1.253, local AS number 100
BGP table version is 338, main routing table version 338
337 network entries using 48528 bytes of memory
2353 path entries using 188240 bytes of memory
100/100 BGP path/bestpath attribute entries using 13600 bytes of memory
33 BGP AS-PATH entries using 1428 bytes of memory
47 BGP community entries using 1596 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 253392 total bytes of memory
1152 received paths for inbound soft reconfiguration
BGP activity 337/0 prefixes, 2354/1 paths, scan interval 60 secs
 
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.3   4        200     692     585      338    0    0 00:39:19      288
192.168.1.4   4        200     692     585      338    0    0 00:39:20      288
192.168.1.19  4        200     690     585      338    0    0 00:39:10      288
192.168.1.20  4        200     690     585      338    0    0 00:39:13      288
R1#sh ip proto | s bgp
  Redistributing: static, bgp 100
Routing Protocol is "bgp 100"
  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
    192.168.1.3                                    4000
    192.168.1.4                                    2000
    192.168.1.19                                   3000
    192.168.1.20                                   1000
  Maximum path: 2
  Routing Information Sources:
    Gateway         Distance      Last Update
    192.168.1.3         20      00:41:47
  Distance: external 20 internal 200 local 200
  Redistributing: bgp 100, rip
R1#

 

R1#sh ip bgp sum     

BGP router identifier 192.168.1.253, local AS number 100

BGP table version is 338, main routing table version 338

337 network entries using 48528 bytes of memory

2353 path entries using 188240 bytes of memory

100/100 BGP path/bestpath attribute entries using 13600 bytes of memory

33 BGP AS-PATH entries using 1428 bytes of memory

47 BGP community entries using 1596 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 253392 total bytes of memory

1152 received paths for inbound soft reconfiguration

BGP activity 337/0 prefixes, 2354/1 paths, scan interval 60 secs

 

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

192.168.1.3   4        200     692     585      338    0    0 00:39:19      288

192.168.1.4   4        200     692     585      338    0    0 00:39:20      288

192.168.1.19  4        200     690     585      338    0    0 00:39:10      288

192.168.1.20  4        200     690     585      338    0    0 00:39:13      288

R1#sh ip proto | s bgp

  Redistributing: static, bgp 100

Routing Protocol is "bgp 100"

  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

    192.168.1.3                                    4000

    192.168.1.4                                    2000

    192.168.1.19                                   3000

    192.168.1.20                                   1000

  Maximum path: 2

  Routing Information Sources:

    Gateway         Distance      Last Update

    192.168.1.3         20      00:41:47

  Distance: external 20 internal 200 local 200

  Redistributing: bgp 100, rip

R1#

 

Thanks& Regards,

George

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Jose Jara
Level 3
Level 3

‎02-09-2015 02:12 PM

Hello George,

it is because it appears the neighbor that is feeding the RIB, so the prefixes received from this neighbor are the best in the BGP table and therefore those ones that will be installed in the route table:

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_pi/command/iri-cr-book/iri-cr-s1.html#wp3837273515

Routing Information Sources:

Lists all the routing sources that the Cisco IOS software is using to build its routing table. The following is displayed for each source:

  • IP address
  • Administrative distance
  • Time the last update was received from this source

Hope this helps,

Jose.

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Go to solution
Jose Jara
Level 3
Level 3

‎02-09-2015 02:12 PM

Hello George,

it is because it appears the neighbor that is feeding the RIB, so the prefixes received from this neighbor are the best in the BGP table and therefore those ones that will be installed in the route table:

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_pi/command/iri-cr-book/iri-cr-s1.html#wp3837273515

Routing Information Sources:

Lists all the routing sources that the Cisco IOS software is using to build its routing table. The following is displayed for each source:

  • IP address
  • Administrative distance
  • Time the last update was received from this source

Hope this helps,

Jose.

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Go to solution
George Joseph
Level 1
Level 1

‎02-10-2015 01:42 AM

Hello Jose,

Makes sense. I've verified all the received routes from those 4 neighbors and looks like all neighbors receiving same routes and 192.168.1.3 is the preferred path for all those routes as it has heigher weight:) I upgraded the device few days back and noticed that the other 3 neighbors disappeared from the routing information source after the upgrade (looks like uptime for that device was more than 1year and routes were preferred alternative paths whenever there was issues on the primary link- which is the reason they all appeared under the routing information source before the upgrade).

 

Cheers!

George

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