VJX 0,1,3 are setup to be RR’s for this simple test , i want to know why link p5 is always preferred even though the physical next-hop changes , and the IGP path to the next-hop is is not via p5 ...
Below baseline exhibits where VJX4 has 3 equal iBGP paths to 77/22 where 172.65.65.11 – VJX1 is the current preferred path
root@VJX4> show route 77/22
inet.0: 17 destinations, 19 routes (17 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
77.0.0.0/22 *[BGP/170] 04:43:01, MED 999, localpref 100, from 172.16.65.10
AS path: I, validation-state: unverified
to 10.0.0.10 via ge-0/0/1.0 (P3)
to 10.0.0.8 via ge-0/0/2.0 (P4)
> to 10.0.0.12 via ge-0/0/3.0 (P5)
[BGP/170] 23:35:18, MED 999, localpref 100, from 172.16.65.11
AS path: I, validation-state: unverified
to 10.0.0.10 via ge-0/0/1.0 (P3)
to 10.0.0.8 via ge-0/0/2.0 (P4)
> to 10.0.0.12 via ge-0/0/3.0 (p5)
[BGP/170] 04:43:06, MED 999, localpref 100, from 172.16.65.13
AS path: I, validation-state: unverified
to 10.0.0.10 via ge-0/0/1.0 (P3)
to 10.0.0.8 via ge-0/0/2.0 (P4)
> to 10.0.0.12 via ge-0/0/3.0 (p5)
root@VJX4> show route 77/22 extensive
inet.0: 17 destinations, 19 routes (17 active, 0 holddown, 0 hidden)
77.0.0.0/22 (3 entries, 1 announced)
TSI:
KRT in-kernel 77.0.0.0/22 -> {indirect(262143)}
*BGP Preference: 170/-101
Next hop type: Indirect
Address: 0x92a8698
Next-hop reference count: 5
Source: 172.16.65.10
Next hop type: Router, Next hop index: 262144
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0, selected (P5)
Session Id: 0x5
Protocol next hop: 172.16.65.12
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
State: <Active Int Ext>
Local AS: 1234 Peer AS: 1234
Age: 4:43:14 Metric: 999 Metric2: 20
Validation State: unverified
Task: BGP_1234.172.16.65.10+56241
Announcement bits (2): 0-KRT 4-Resolve tree 4
AS path: I (Originator)
Cluster list: 0.0.0.0
Originator ID: 172.16.65.12
Accepted
Localpref: 100
Router ID: 172.16.65.10
Indirect next hops: 1
Protocol next hop: 172.16.65.12 Metric: 20
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
Indirect path forwarding next hops: 3
Next hop type: Router
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0 (P5)
Session Id: 0x5
172.16.65.12/32 Originating RIB: inet.0
Metric: 20 Node path count: 1
Forwarding nexthops: 3
Nexthop: 10.0.0.10 via ge-0/0/1.0 (P3)
BGP Preference: 170/-101
Next hop type: Indirect
Address: 0x92a8698
Next-hop reference count: 5
Source: 172.16.65.11
Next hop type: Router, Next hop index: 262144
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0, selected ( P5 )
Session Id: 0x5
Protocol next hop: 172.16.65.12
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Update source
Local AS: 1234 Peer AS: 1234
Age: 23:35:31 Metric: 999 Metric2: 20
Validation State: unverified
Task: BGP_1234.172.16.65.11+60823
AS path: I (Originator)
Cluster list: 1.1.1.1
Originator ID: 172.16.65.12
Accepted
Localpref: 100
Router ID: 172.16.65.11
Indirect next hops: 1
Protocol next hop: 172.16.65.12 Metric: 20
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
Indirect path forwarding next hops: 3
Next hop type: Router
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0 (P5)
Session Id: 0x5
172.16.65.12/32 Originating RIB: inet.0
Metric: 20 Node path count: 1
Forwarding nexthops: 3
Nexthop: 10.0.0.10 via ge-0/0/1.0
BGP Preference: 170/-101
Next hop type: Indirect
Address: 0x92a8698
Next-hop reference count: 5
Source: 172.16.65.13
Next hop type: Router, Next hop index: 262144
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0, selected (P5)
Session Id: 0x5
Protocol next hop: 172.16.65.12
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
State: <NotBest Int Ext>
Inactive reason: Not Best in its group - Update source
Local AS: 1234 Peer AS: 1234
Age: 4:43:19 Metric: 999 Metric2: 20
Validation State: unverified
Task: BGP_1234.172.16.65.13+52655
AS path: I (Originator)
Cluster list: 3.3.3.3
Originator ID: 172.16.65.12
Accepted
Localpref: 100
Router ID: 172.16.65.13
Indirect next hops: 1
Protocol next hop: 172.16.65.12 Metric: 20
Indirect next hop: 94ec000 262143 INH Session ID: 0x4
Indirect path forwarding next hops: 3
Next hop type: Router
Next hop: 10.0.0.10 via ge-0/0/1.0 (P3)
Session Id: 0x1
Next hop: 10.0.0.8 via ge-0/0/2.0 (P4)
Session Id: 0x3
Next hop: 10.0.0.12 via ge-0/0/3.0 (P5)
Session Id: 0x5
172.16.65.12/32 Originating RIB: inet.0
Metric: 20 Node path count: 1
Forwarding nexthops: 3
Nexthop: 10.0.0.10 via ge-0/0/1.0 (P3)
root@VJX4> show route 172.16.65.10
inet.0: 17 destinations, 19 routes (17 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.65.10/32 *[IS-IS/18] 04:45:50, metric 10
> to 10.0.0.8 via ge-0/0/2.0 (P4)
root@VJX4> show route 172.16.65.12
inet.0: 17 destinations, 19 routes (17 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.65.12/32 *[IS-IS/18] 04:45:59, metric 20
> to 10.0.0.10 via ge-0/0/1.0 (P3)
to 10.0.0.8 via ge-0/0/2.0 (P4)
to 10.0.0.12 via ge-0/0/3.0 (P5)