IOS-XR BGP best path selection

[KirylAviaryanau5293]

Hi everyone,

Could someone please explain, why second path is best? I'd appreciate any advice or useful links.

Thanks in advance.

BGP routing table entry for 0.0.0.0/0, Route Distinguisher: 65000:20
Versions:
Process bRIB/RIB SendTblVer
Speaker 1317286004 1317286004
Last Modified: Nov 16 02:42:09.323 for 1w1d
Paths: (3 available, best #2)
Not advertised to any peer
Path #1: Received by speaker 0
Not advertised to any peer
Local
10.254.89.61 from 0.0.0.0 (10.254.90.19)
Origin incomplete, metric 11264, localpref 100, weight 32768, valid, redistributed
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:20190
Extended community: COST:128:129:11264 EIGRP route-info:0x0:0 EIGRP AD:10:538 EIGRP RHB:255:2:256 EIGRP LM:0x0:1:1500 EIGRP AR:10:10.254.89.24 EIGRP PM:3:0 RT:65000:20 RT:65000:2000
Path #2: Received by speaker 0
Not advertised to any peer
Local
10.254.90.9 (metric 9) from 10.254.156.1 (10.254.90.9)
Received Label 492312
Origin incomplete, metric 3328, localpref 50, valid, internal, best, group-best, import-candidate, not-in-vrf
Received Path ID 0, Local Path ID 1, version 1317286004
Community: 65000:20190
Extended community: COST:128:129:3328 EIGRP route-info:0x0:0 EIGRP AD:10:768 EIGRP RHB:255:2:2560 EIGRP LM:0x0:1:1500 EIGRP AR:10:10.254.89.23 EIGRP PM:3:0 RT:65000:20 RT:65000:2000
Originator: 10.254.90.9, Cluster list: 10.254.156.1
Path #3: Received by speaker 0
Not advertised to any peer
Local
10.254.90.9 (metric 9) from 10.254.156.7 (10.254.90.9)
Received Label 492312
Origin incomplete, metric 3328, localpref 50, valid, internal, import-candidate, not-in-vrf
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:20190
Extended community: COST:128:129:3328 EIGRP route-info:0x0:0 EIGRP AD:10:768 EIGRP RHB:255:2:2560 EIGRP LM:0x0:1:1500 EIGRP AR:10:10.254.89.23 EIGRP PM:3:0 RT:65000:20 RT:65000:2000
Originator: 10.254.90.9, Cluster list: 10.254.156.7

[Harold Ritter]

Hi @KirylAviaryanau5293 ,

You can use the keyword "bestpath-compare" to get more information about why bgp selected a given path.

show bgp ipv4 unicast 0.0.0.0/0 bestpath-compare

Here's an example:

RP/0/0/CPU0:R1#show bgp ipv4 unicast 0.0.0.0/0 bestpath-compare
Wed Nov 24 14:11:33.577 UTC
BGP routing table entry for 0.0.0.0/0
Versions:
Process bRIB/RIB SendTblVer
Speaker 6 6
Last Modified: Nov 24 13:54:54.521 for 00:16:39
Paths: (2 available, best #1)
Advertised IPv4 Unicast paths to update-groups (with more than one peer):
0.2
Path #1: Received by speaker 0
Advertised IPv4 Unicast paths to update-groups (with more than one peer):
0.2
2
192.168.12.2 from 192.168.12.2 (192.168.100.2)
Origin IGP, metric 0, localpref 100, valid, external, best, group-best
Received Path ID 0, Local Path ID 1, version 5
Origin-AS validity: (disabled)
best of AS 2, Overall best
Path #2: Received by speaker 0
Not advertised to any peer
3
192.168.13.3 from 192.168.13.3 (192.168.100.3)
Origin IGP, metric 0, localpref 100, valid, external, group-best
Received Path ID 0, Local Path ID 0, version 0
Origin-AS validity: (disabled)
best of AS 3
Higher router ID than best path (path #1) <+++++++++++++++++
RP/0/0/CPU0:R1#

Regards,

[KirylAviaryanau5293]

It has worked. Thanks a lot.

[paul driver]

Hello
I would say path two is selected over path three due to lowest cluster-id ( router id)  - Curious to what does best path shows?