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BGP Best Path Selection Question

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Hi There,


I'm doing a practice CCIE lab and I'm still struggling a little with the BGP best path selection process. Can anyone tell me what path attribute causes the best route to be selected from the following output? Please note that the router with BGP router-id of is a an IBGP peer. The other two are eBGP peers. Also, why does the route with a next hop of have an empty metric attribute and how is this compared to the metrics of zero?


Rack11R6#show ip bgp
BGP table version is 11, local router ID is
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
* i28.119.16.0/24 0 100 0 54 i
* 0 0 54 i
*> 0 54 i
Rack11R6#show ip bgp
BGP routing table entry for, version 2
Paths: (3 available, best #3, table Default-IP-Routing-Table)
Advertised to update-groups:
1 2
54 from (
Origin IGP, metric 0, localpref 100, valid, internal
54 from (
Origin IGP, metric 0, localpref 100, valid, external
54 from (
Origin IGP, localpref 100, valid, external, best


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I am thinking : 1st external wins over internal; then oldest route


MED -or metric- have some restrictions and extra commands like med deterministic, always-compare med, missing med as worst;

show run all or full to see hidden and/or default bgp commands ; some routers or cisco routers default behavior is to assign a value of 0 to the missing MED. so, in your case, med is not being compared at all.

Edited by martinlo

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