Understanding "show ip bgp summary" output

Answered Question
Oct 26th, 2012

Could someone please explain some of the lines of output from the command run below please.

The line that starts "424983 network entries..."; What does that mean? If I add up how many routes each peer is advertising me, it is more than this but oviously some are advertising the same routes. Is that how many have made it into the RIB?

The line that starts "525139 path entries..."; What are path entries if they aren't routes? Whats the difference between these two, is that to total number of routes received, duplicates included?

Those two confuse me the most I think, but ultimately, is there page somewhere I can seee what every line means?

Thank you.

R1>show bgp ipv4 unicast summary

BGP router identifier 10.0.64.1, local AS number 11111

BGP table version is 456732550, main routing table version 456732550

424983 network entries using 51847926 bytes of memory

525139 path entries using 27307228 bytes of memory

78207/72451 BGP path/bestpath attribute entries using 5943732 bytes of memory

6 BGP rrinfo entries using 144 bytes of memory

64596 BGP AS-PATH entries using 2210108 bytes of memory

4342 BGP community entries using 330426 bytes of memory

13 BGP extended community entries using 328 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 87639892 total bytes of memory

Dampening enabled. 209 history paths, 111 dampened paths

28 received paths for inbound soft reconfiguration

BGP activity 8379913/7954718 prefixes, 488102372/487576978 paths, scan interval 60 secs

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

10.224.0.6      4 65013   37281   36372 456732556    0    0 2d03h           2

10.0.30.53     4 22222 2825586   19277 456732541    0    0 1w5d       159648

10.0.224.129   4 11111 2870058 2061843 456732556    0    0 1w5d        52904

10.0.224.135   4 11111 2451224 2061733 456732556    0    0 1w5d       262535

10.0.224.137   4 11111   19280 3808184 456732556    0    0 1w5d           30

10.0.224.138   4 11111   19323 3808184 456732556    0    0 1w5d          110

10.0.224.141   4 11111 1792201 3808355 456732556    0    0 1w5d        49596

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

10.0.227.75    4 65003  102654  110352 456732541    0    0 1w5d           11

10.0.228.17    4 65010   37280   36372 456732566    0    0 2d03h           8

10.0.229.38    4 65007       0       0        0    0    0 11w5d    Idle

10.0.229.223   4 65002   37281   36372 456732566    0    0 2d03h           1

10.0.234.133   4 65005  105138  110376 456732541    0    0 1w5d            2

10.0.234.135   4 65006  105134  110368 456732541    0    0 1w5d            2

10.0.241.145   4 65011   37282   36373 456732566    0    0 2d03h           2

I have this problem too.
0 votes
Correct Answer by ajay chauhan about 1 year 5 months ago

424983 network entries using 51847926 bytes of memory

525139 path entries using 27307228 bytes of memory

BGP always choose best path correct ? so 424983 mean these many of routes as of now.Running multihomed network mean for one destination multiple path can exist ? right so 2nd entry says that how many paths .

BGP table version is 456732550

Everytime routes comes in or deleted this will keep incrementing .

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

10.224.0.6 4 65013 37281 36372 456732556 0 0 2d03h 2

In this o/p who is your bgp running neighbor here -10.224.0.6 then BGP version which is 4,what AS number is running 65013. Up/down session Up time and how many prefix being learned = 2 .

Thanks

Ajay

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Correct Answer
ajay chauhan Sun, 10/28/2012 - 02:51

424983 network entries using 51847926 bytes of memory

525139 path entries using 27307228 bytes of memory

BGP always choose best path correct ? so 424983 mean these many of routes as of now.Running multihomed network mean for one destination multiple path can exist ? right so 2nd entry says that how many paths .

BGP table version is 456732550

Everytime routes comes in or deleted this will keep incrementing .

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

10.224.0.6 4 65013 37281 36372 456732556 0 0 2d03h 2

In this o/p who is your bgp running neighbor here -10.224.0.6 then BGP version which is 4,what AS number is running 65013. Up/down session Up time and how many prefix being learned = 2 .

Thanks

Ajay

milan.kulik Sun, 10/28/2012 - 04:34

Hi,

I'd recommend an excellent book

http://www.amazon.com/BGP-Design-Implementation-Randy-Zhang/dp/1587051095

which says on page 56:

"Cisco IOS software keeps track of three structures related to BGP: the BGP RIB, the IP

RIB, and the IP CEF. The BGP RIB is used to store prefixes received via BGP in addition

to their associated attributes, which include communities, AS_PATH, and so on. A BGP

speaker may have multiple BGP sessions with an assortment of iBGP and eBGP peers,

resulting in the potential for multiple paths per prefix. Each unique prefix is stored in the

BGP network table, and all the paths for the same prefix are stored as BGP path entries. The

amount of memory that each prefix (or network) and path entry consumes may vary from

release to release.

The show ip bgp summary output provides memory use for certain BGP components.

With Cisco IOS software Release 12.0(15)S1, each unique prefix uses 129 bytes, and each

additional path consumes another 36 bytes. For example, if the BGP RIB has 100 prefixes

and 200 paths, the total memory for these entries is (100 * 129) + (100 * 36) = 16,500 bytes.

The output also contains the memory use for path attributes, community, caches, and so on,

depending on the BGP configuration and prefixes received from peers."

HTH,

Milan

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