metric values in BGP

[axfalk]

R1#sh ip bgp 170.190.140.0 255.255.255.0

BGP routing table entry for 170.190.140.0/24, version 1324996

Paths: (2 available, best #2, table Default-IP-Routing-Table)

Multipath: eBGP

Not advertised to any peer

64806 64872 64852 64851 64871 64811 65531 64812

10.16.70.122 (metric 6) from 10.16.70.122 (10.23.127.8)

Origin IGP, metric 0, localpref 100, valid, internal

There're 2 metric values (0 & 6) in the above BGP statement..Can someone please tell me what do they pertain to?

Thanks...

[Konstantin Dunaev]

10.16.70.122 (metric 6)

- IGP (OSPF, ISIS, RIP....) metric

Origin IGP, metric 0, localpref 100, valid, internal

- BGP metric, or MED value (default is 0)

[axfalk]

Thanks for your response...

R1#sh ip bgp 170.190.140.0 255.255.255.0

BGP routing table entry for 170.190.140.0/24, version 1324996

Paths: (2 available, best #2, table Default-IP-Routing-Table)

Multipath: eBGP

Not advertised to any peer

64806 64872 64852 64851 64871 64811 65531 64812

10.16.70.122 (metric 6) from 10.16.70.122 (10.23.127.8)

Origin IGP, metric 0, localpref 100, valid, internal

64806 64872 64852 64851 64871 64811 65531 64812

10.16.60.14 (metric 6) from 10.123.127.7 (10.23.127.7)

Origin IGP, metric 0, localpref 100, valid, internal, best

So, if the BGP metrics are identical between the 2 routes above, why is the second route the best one? Thnx again...

[Jerry Ye]

axfalk,

Can you posted the output of "show ip bgp summary"? It is possible that 10.123.127.7 established the BGP session with your router first (#10). If the up time for both peers are the same. Then it is choosing the lower's BGP router ID - 10.123.127.7 (#11).

Please check out the link which explain the BGP Best Path Selection Algorithm.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

HTH,

jerry

[Konstantin Dunaev]

in your example all BGP attributes for both pathes are identical it means that 2 last tiebreakers decide which path will be the best, they are the smalles router-id and the smallest neighbor id.

in your case the router with router-id 10.23.127.7 was choosed.