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[Junos] BFD SNMP trap under Link Category in SNMP V2

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Article ID: KB31664 KB Last Updated: 29 Jul 2020Version: 3.0
Summary:

This article explains the Bidirectional Forwarding Detection (BFD) trap generated to the Network Management Server (NMS) when 'routing' category is configured under 'trap-group' options.

Symptoms:

According to Juniper Networks Enterprise-Specific SNMP Version 2 Traps, BFD traps should be generated under the 'routing' category. However, when routing category is used, BFD traps are not generated.

Cause:

Consider the following topology:

 _______________                                         _______________ 
|               |                                       |               | 
|     MX-104    |ge-0/0/2_____199.1.1.0/24______ge-0/0/3|     MX-480    |
|               |.1                                   .2|               |
|_______________|                                       |_______________|
              

OSPF is running between the routers. Both routers are 0 and we have established BFD session for OSPF interface.
 
Below is the configuration from MX-104:
 
[MASTER]
root@104> show configuration interfaces ge-0/0/2
Apr 25 06:35:48
unit 0 {
    family inet {
        address 199.1.1.1/24;
    }
}
 
[MASTER]
root@104> show configuration protocols ospf area 0 interface ge-0/0/2.0
Apr 25 06:35:50
bfd-liveness-detection {
    minimum-interval 300;
    multiplier 3;
    full-neighbors-only;
}
 

Below is the configuration from MX-480:
 
root@480> show configuration interfaces ge-0/0/3
Apr 25 12:06:37
unit 0 {
    family inet {
        address 199.1.1.2/24;
    }
}
 
root@480> show configuration protocols ospf area 0 interface ge-0/0/3
Apr 25 12:06:38
bfd-liveness-detection {
    minimum-interval 300;
    multiplier 3;
    full-neighbors-only;
}
 
The outputs below show the 'routing' category under trap-group configuration and the exit interface for SNMP traps to be sent to the SNMP server:
 
root@480> show configuration snmp trap-group q
Apr 25 12:07:48
version v2;
categories {
    routing;
}
targets {
    172.17.31.81; <--- SNMP server address
}
 
root@480> show route 172.17.31.81
 
inet.0: 20 destinations, 20 routes (20 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
 
0.0.0.0/0          *[Static/5] 1w4d 00:45:24
                    > to 10.219.37.193 via fxp0.0
 
The following output shows deactivation of BFD to simulate BFD down trap to the SNMP server:
 
[MASTER][edit]
root@104# show | compare
Apr 25 10:48:55
[edit protocols ospf area 0.0.0.0 interface ge-0/0/2.0]
!       inactive: bfd-liveness-detection { ... }
 
[MASTER][edit]
root@104# commit
Apr 25 10:48:58
re1:
configuration check succeeds
re0:
configuration check succeeds
commit complete
re1:
commit complete
 
Monitoring the interface through which NMS Server is reachable on SNMP port (162) shows no output indicating BFD down trap is not being generated or sent to the SNMP server
 
root@480> monitor traffic interface fxp0 extensive matching "port 162"
Apr 25 16:36:34
Address resolution is ON. Use <no-resolve> to avoid any reverse lookup delay.
Address resolution timeout is 4s.
Listening on fxp0, capture size 1514 bytes
 
^C
97 packets received by filter
0 packets dropped by kernel
 
The following output shows BFD has gone down due to deactivation on the remote end:
 
root@480> show bfd session
Apr 25 16:37:47
                                                  Detect   Transmit
Address                  State     Interface      Time     Interval  Multiplier
199.1.1.1                Down      ge-0/0/3.0     3.000     2.000        3
 
1 sessions, 1 clients
Cumulative transmit rate 0.5 pps, cumulative receive rate 1.0 pps
Solution:

The 'link' category under trap-group must be enabled for BFD traps to be generated and sent to the SNMP server:

root@480> show configuration snmp trap-group q
Apr 25 12:14:38
version v2;
categories {
    link;
}
targets {
    172.17.31.81;
}
 
The following output shows BFD is deactivated again to simulate BFD down trap:
 
[MASTER][edit]
root@104# show | compare
Apr 25 11:16:49
[edit protocols ospf area 0.0.0.0 interface ge-0/0/2.0]
!       inactive: bfd-liveness-detection { ... }
 
[MASTER][edit]
root@104# commit
Apr 25 11:17:01
re1:
configuration check succeeds
re0:
configuration check succeeds
commit complete
re1:
commit complete
 
Monitoring the interface through which SNMP server is reachable on SNMP port shows BFD traps being sent out:
 
root@480> monitor traffic interface fxp0 extensive matching "port 162"
Apr 25 16:46:58
Address resolution is ON. Use <no-resolve> to avoid any reverse lookup delay.
Address resolution timeout is 4s.
Listening on fxp0, capture size 1514 bytes
 
16:47:20.507089 Out
        Juniper PCAP Flags [Ext], PCAP Extension(s) total length 16
          Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
          Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
          Device Interface Index Extension TLV #1, length 2, value: 64
          Logical Interface Index Extension TLV #4, length 4, value: 5
        -----original packet-----
Reverse lookup for 172.17.31.81 failed (check DNS reachability).
Other reverse lookup failures will not be reported.
Use <no-resolve> to avoid reverse lookups on IP addresses.
 
        00:a0:a5:91:15:4a > 00:00:5e:00:01:13, ethertype IPv4 (0x0800), length 263: (tos 0x0, ttl  64, id 10860, offset 0, flags [none], proto: UDP (17), length: 249) 10.219.37.210.58355 > 172.17.31.81.snmptrap: [udp sum ok]  |30|81|da|02|01SNMPv2c |04|01C=q |a7|81|d1V2Trap(209)|02|04|02|01|02|01|30|81|c2 |30|10|06|08system.sysUpTime.0=|43|04113724900 |30|1a|06|0aS:1.1.4.1.0=|06|0cE:2636.5.3.1.0.2 |30|14|06|0fE:2636.5.3.1.1.2.1.8.53=|42|014 |30|14|06|0fE:2636.5.3.1.1.2.1.8.53=|42|014 |30|14|06|0fE:2636.5.3.1.1.2.1.13.53=|02|011 |30|17|06|0fE:2636.5.3.1.1.2.1.14.53=|04|04c7_01_01_01 |30|1b|06|0dE:2636.3.45.1.2.1.0=|04|0a"ge-0/0/3.0" |30|1a|06|0aS:1.1.4.3.0=|06|0cE:2636.1.1.1.2.25
^C
69 packets received by filter
0 packets dropped by kernel
 

root@480> show bfd session
Apr 25 16:48:15
                                                  Detect   Transmit
Address                  State     Interface      Time     Interval  Multiplier
199.1.1.1                Down      ge-0/0/3.0     3.000     2.000        3
 
1 sessions, 1 clients
Cumulative transmit rate 0.5 pps, cumulative receive rate 1.0 pps
 
From the above output, 0FE:2636.5.3 indicates the OIDs used for BFD and traps related to BFD are exiting the fxp0 interface which is the exit interface for the SNMP server.
Modification History:

2020-07-29: Reviewed for accuracy and no changes needed.
2017-05-19: Minor edit. Non-technical

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