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[EOL/EOE] Change of behavior in BGP notification messages between Junos 12.3 and 13.3

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Article ID: KB32113 KB Last Updated: 26 Oct 2020Version: 2.0
Summary:

Note: A product listed in this article has either reached hardware End of Life (EOL) OR software End of Engineering (EOE).  Refer to End of Life Products & Milestones for the EOL, EOE, and End of Support (EOS) dates.



This articles explains the difference in syslog messages between Junos 12.3 and 13.3 regarging the generation of BGP notification messages by a device for any unconfigured peer's connection attempt.

Symptoms:

Consider the following topology:

Case 1

R1 ----------------------------------------------- R2.                                   

R1's configuration has R2 as BGP peer:

root@R1> show configuration system syslog file messages 
any any;

root@R1> show interfaces terse fxp0      
Interface               Admin Link Proto    Local                 Remote
fxp0                    up    up
fxp0.0                  up    up   inet     10.219.37.219/26

root@R1> show configuration protocols bgp 
group kb {
    type internal;
    local-address 10.219.37.219;
    neighbor 10.219.22.222;
}
root@R1> show configuration routing-options autonomous-system 
65015;

R2 running on Junos 12.3R4.6, where R1 is not configured as its neighbor:

root@R2> show version 
Hostname: R2
Model: mx80
JUNOS Base OS boot [12.3R6]

root@R2> show configuration system syslog file messages   
any any;

root@R2> show interfaces terse fxp0   
Interface               Admin Link Proto    Local                 Remote
fxp0                    up    up
fxp0.0                  up    up   inet     10.219.22.222/26

 
root@R2> show configuration routing-options autonomous-system 
65015;

root@R2> show configuration protocols bgp 
group kb {
    type internal;
    local-address 10.219.22.222;
}

When R1 tries to establish BGP with R2 as per the above configuration, BGP will be stuck in active state as below:

root@R1> show bgp summary    
Groups: 1 Peers: 1 Down peers: 1
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
inet.0               
                       0          0          0          0          0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
10.219.22.222         65015          0          1       0       0          24 Active

Further the R1 log message will show BGP connection is not getting established. However the reason is unclear.

Sep  7 23:29:13.683  R1 rpd[5551]: bgp_recv: peer 10.219.22.222 (Internal AS 65015): received unexpected EOF

From the log messages of R2, a message is logged which will indicates why the configuration is rejected. However, a notification message is not generated by R2 to be sent to R1:

Sep  7 23:29:13.678 2017  R2 rpd[1380]: bgp_listen_accept: Connection attempt from unconfigured neighbor: 10.219.37.219+61487

 

Solution:

Starting with Junos 13.3, enhancements to log messages have been added for R2 to send a notification message that will provide the exact reason why BGP is not getting established.

Considering the same topology:

R1 ----------------------------------------------- R2

root@R1> show configuration system syslog file messages 
any any;

root@R1> show interfaces terse fxp0      
Interface               Admin Link Proto    Local                 Remote
fxp0                    up    up
fxp0.0                  up    up   inet     10.219.37.219/26

root@R1> show configuration protocols bgp 
group kb {
    type internal;
    local-address 10.219.37.219;
    neighbor 10.219.22.222;
}
root@R1> show configuration routing-options autonomous-system 
65015

R2 is running on Junos 13.3 (or above) and R1 is not configured as  BGP peer/neighbor under BGP configuration of R2:

root@R2> show version 
Hostname: R2
Model: mx80
JUNOS Base OS boot [13.3R6.5]

root@R2> show configuration system syslog file messages   
any any;

root@R2> show interfaces terse fxp0   
Interface               Admin Link Proto    Local                 Remote
fxp0                    up    up
fxp0.0                  up    up   inet     10.219.22.222/26

root@R2> show configuration routing-options autonomous-system 
65015

root@R2> show configuration protocols bgp 
group kb {
    type internal;
    local-address 10.219.22.222;
}
root@R2> show bgp summary 
Groups: 1 Peers: 1 Down peers: 1
Table          Tot Paths  Act Paths Suppressed    History Damp State    Pending
inet.0               
                       0          0          0          0          0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
10.219.22.222       65015          0          2       0       0       19:12 Active

Log messages in R2 clearly shows a notification message being generated and sent as unicast to R1:

Sep  7 23:52:29  R2 rpd[1380]: bgp_listen_accept: Connection attempt from unconfigured neighbor: 10.219.37.219+52956
Sep  7 23:52:29  R2 rpd[1380]: bgp_listen_accept:4572: NOTIFICATION sent to 10.219.37.219+52956 (proto): code 6 (Cease) subcode 5 (Connection Rejected), Reason: Connection attempt from unconfigured neighbor: 10.219.37.219+52956

Log messages in R1 indicate that BGP connection is rejected by the peer device:

Sep  7 23:52:29  R1 rpd[5551]: bgp_recv_open: peer 10.219.22.222 (Internal AS 65015): received NOTIFICATION code 6 (Cease) subcode 5 (Connection Rejected)
Modification History:
2020-10-23: Article reviewed for accuracy, no changes required; article accurate and valid

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