Log-Neighbor-Changes

Scenario to verify BGP log-neighbor-changes parameter configuration.

By default, BGP does not log neighbor state changes to syslog. The log-neighbor-changes parameter enables logging of BGP neighbor state transitions (up/down) and the reason for the change. This is useful for troubleshooting and monitoring BGP session stability.

In this test, DUT0 (AS 20) establishes an iBGP session with DUT1 (AS 20) with log-neighbor-changes enabled. After the session is established, a shutdown is applied to trigger a state change. The test then verifies that the neighbor change event appears in the system logs.

Test BGP Log Neighbor Changes

Description

This test verifies that log-neighbor-changes causes BGP to log neighbor state transitions to syslog. After establishing an iBGP session with the parameter enabled, a shutdown is applied to the neighbor on DUT0, and the system logs are checked for the neighbor change event.

Scenario

Note

Configure iBGP with log-neighbor-changes enabled on DUT0.

Step 1: Set the following configuration in DUT0 :

set interfaces ethernet eth0 address 10.10.0.100/24
set protocols bgp 20 neighbor peer remote-address 10.10.0.200
set protocols bgp 20 neighbor peer remote-as 20
set protocols bgp 20 parameters log-neighbor-changes
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'
set system syslog global level info

Step 2: Set the following configuration in DUT1 :

set interfaces ethernet eth0 address 10.10.0.200/24
set protocols bgp 20 neighbor peer remote-address 10.10.0.100
set protocols bgp 20 neighbor peer remote-as 20
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Attention

Verify iBGP session establishes between DUT0 and DUT1.

Step 3: Run command protocols bgp show ip summary at DUT0 and check if output matches the following regular expressions:

10.10.0.200.*Established

Show output

IPv4 Unicast Summary:
BGP router identifier 10.10.0.100, local AS number 20 VRF default vrf-id 0
BGP table version 0
RIB entries 0, using 0 bytes of memory
Peers 1, using 24 KiB of memory

Neighbor        LocalAddr       V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down        State   PfxRcd   PfxSnt Desc
10.10.0.200     10.10.0.100     4         20         3         3        0    0    0 00:00:01  Established        0        0 FRRouting/10.4.1

Total number of neighbors 1

Note

Apply shutdown on DUT0 neighbor to trigger a state change event.

Step 4: Modify the following configuration lines in DUT0 :

set protocols bgp 20 neighbor peer shutdown

Attention

Verify session shows Idle (Admin) after shutdown.

Step 5: Run command protocols bgp show ip summary at DUT0 and check if output matches the following regular expressions:

10.10.0.200.*Idle \(Admin\)

Show output

IPv4 Unicast Summary:
BGP router identifier 10.10.0.100, local AS number 20 VRF default vrf-id 0
BGP table version 0
RIB entries 0, using 0 bytes of memory
Peers 1, using 24 KiB of memory

Neighbor        LocalAddr       V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down        State   PfxRcd   PfxSnt Desc
10.10.0.200     10.10.0.100     4         20         3         4        0    0    0 00:00:01 Idle (Admin)        0        0 FRRouting/10.4.1

Total number of neighbors 1

Attention

Verify the neighbor change event is logged in syslog.

Step 6: Run command file show running://log/messages | grep ADJCHANGE at DUT0 and check if output contains the following tokens:

%ADJCHANGE: neighbor 10.10.0.200(osdx) in vrf default Down Admin. shutdown

Show output

2026-03-05 14:59:22.989846 daemon-info , bgpd[150742]:  [N9HHH-F8H1M] %ADJCHANGE: neighbor 10.10.0.200(osdx) in vrf default Up
2026-03-05 14:59:24.753548 daemon-info , bgpd[150742]:  [PXVXG-TFNNT] %ADJCHANGE: neighbor 10.10.0.200(osdx) in vrf default Down Admin. shutdown

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