BGP Difference in prefix count

nedk12345 · ‎12-12-2009

hello, here's output of show ip bgp summary and show ip bgp neighbour. i am confused why output shows different numbers. is there a link that will give complete explanation of command output and why numbers is different

1. why is there a difference between in so many places between prefix recvd. For eg. 322752 network entries (3d line) in bgp summary wheras at the bottom of show ip bgp summary it says that prefix received was 300115

2. Is there difference between network entries, path entries

3. What is 58835/58158 BGP path/bestpath in show ip bgp summary

4. In sho ip bgp summary the prefix recvd from neighbor says 300115 however in show ip bgp neighbor it shows under Prefix activity current prefix is 300125 and total prefix is 549983. where does 549983 come from.this is the show ip bgp neighbor for particular neighbor so should it not show the same number of current recvd prefix and total recvd prefix.

5. in general why is that if you have BGP session with internet than the paths are always so many. if only 1 bgp session than shouldn't there be only 1 path recevd from neighbor.

6. is there a way to see number of paths per prefix per neighbor

thanks

route-server.as3257.net>show ip bgp summary
BGP router identifier 213.200.87.253, local AS number 65534
BGP table version is 5858478, main routing table version 5858478
322752 network entries using 36470976 bytes of memory
300378 path entries using 15619656 bytes of memory
58835/58158 BGP path/bestpath attribute entries using 6354180 bytes of memory
49979 BGP AS-PATH entries using 1337772 bytes of memory
353 BGP community entries using 13260 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 59795844 total bytes of memory
Dampening enabled. 263 history paths, 137 dampened paths
BGP activity 829855/499706 prefixes, 1229644/922229 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
213.200.64.93 4 3257 2271950 110723 5858478 0 0 1d23h 300115
route-server.as3257.net>

route-server.as3257.net>show ip bgp neighbor

For address family: IPv4 Unicast
BGP table version 5857296, neighbor version 5857296/0
Output queue sizes : 0 self, 0 replicated
Index 1, Offset 0, Mask 0x2
1 update-group member
NEXT_HOP is always this router
Outgoing update prefix filter list is denyany
                                 Sent       Rcvd
Prefix activity:               ----       ----
    Prefixes Current:               0     300125 (Consumes 15618824 bytes)
    Prefixes Total:                 0     549883
    Implicit Withdraw:              0     215984
    Explicit Withdraw:              0      33777
    Used as bestpath:             n/a     300038
    Used as multipath:            n/a          0
    History paths:                n/a        238 (Consumes 12376 bytes)

                                   Outbound    Inbound
Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:         501842        n/a
    Total:                           501842          0
Number of NLRIs in the update sent: max 0, min 0

Giuseppe Larosa · ‎12-12-2009

Hello Ned,

the ip routing command reference is the right place to look at for explanation of fields of these show commands

sh ip bgp summary

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp5.html#wp1016342

and sh ip bgp neighbor

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp5.html#wp1041642

About your questions:

>> 322752 network entries using 36470976 bytes of memory

this describes total number of BGP prefixes in the BGP table

x.x.x.x 4 yyy 2271950 110723 5858478 0 0 1d23h 300115

this describes the number of prefixes received by this neighbor, even if this would be the only BGP peer a difference can arise from locally injected BGP routes for example as a result of redistributing an IGP into BGP.

Hope to help

Giuseppe