Description

This article provides a checklist to use when troubleshooting SNMP related issues.

Symptoms

Symptoms :
  • Router not responding to SNMP management station or NMS (Network Management System): 
    Request timeout
Not able to receive bulk-request
Not able to do mib walk on the NMS
Counters not same on router and NMS
  • Unable to find the MIB/OID for a specific parameter on the router
 
  • SNMPD memory leak issues due to SNMPD
 
  • SNMP config errors that result in a variety of symptoms (for example, traps not being generated and so on)

Solution

Note: Please, make sure that the SNMP server is polling form the correct address. For example, using the actual IRB or loopback IP address, instead of the virtual-gateway

 

Click on the following SNMP topics to jump to the corresponding troubleshooting help:


In Junos, SNMPD is the primary agent and it talks to sub-agents to fetch the data. In certain cases, the sub-agents further request the PFE/Kernel or some other daemon for data, in which case, there may be a chance that the NMS/server may see response related issues from the router.

When NMS sends a request to the router, it usually waits for 1 second (default) for the response and if no response is received within 1 second, the request is retransmitted. A higher timeout (5 to 10 seconds) value should be used.

  • The NMS can timeout on a SNMP request for various reasons which include:
  • The NMS request is not reaching or dropped by the SNMPD on the router.
  • The SNMP primary agent or Sub-agent is starved of CPU memory and SNMP packet processing is slow.
  • The sub-agent is dropped the request from primary agent due to some bug in the code.
  • For interface related queries, some interface is slow in responding to the stats request.
  • PFE as a whole is slow in responding to the stats request.

For more information about the SNMP implementation in Junos, refer to the following links:

 

Router not responding to SNMP or response is slow (Response Related Issues):

The following checklist includes tasks that can be performed, when troubleshooting response related issues:

 

  1. Verify network connectivity between router and Network Management System (NMS).  

    Verify that the Network Management System can connect to the router: perform a ping test from Network Management System to the router and vice-versa. SNMP requires that the underlying network, which connects the device to the Network Management System, functions correctly. If the round trip time is unusually high, then there is some issue with the routing in the network. Troubleshoot to check why packets are being delayed.

    If ping works, check if there are any firewalls that deny SNMP traffic; but permit other network traffic to flow freely. UDP 161 port needs to be open to pass SNMP traffic.

    Note:  When a device has multiple IP interfaces, certain device SNMP agents respond from the interface that is closest to the Network Management Station, which makes the request, no matter what interface, to which the SNMP management station makes the request.  Other devices accept requests on any interface, but respond to the request from a specific IP interface. Any firewall will need to be configured to accommodate these behaviors.

 

 

 

 

  • Check if any errors are reported in log messages, log chassisd, and vty outputs of ' show syslog messages ' and ' show nvram '.  Verify if there are any known  PRs  or PSNs that are related to SNMP for Junos routers and which matches the issue being experienced.

 

MIB/OID References:

The following references include answers to MIB/OID related questions:
 

Standard MIB’s/OID’s that Junos supports:
http://www.juniper.net/techpubs/en_US/junos/topics/reference/standards/snmp-std-mibs-junos-nm.html

Juniper enterprise specific MIBs:
http://www.juniper.net/techpubs/en_US/junos/information-products/pathway-pages/mibs-and-traps-ref/mibs-and-traps-ref.html#enterprise-specific-mibs
or
http://www.juniper.net/techpubs/en_US/junos/topics/concept/juniper-specific-mibs-junos-nm.html

Enterprise specific MIBs and the supported Junos devices:
http://www.juniper.net/techpubs/en_US/junos/topics/reference/general/enterprise-specific-mibs-platform-support-junos-nm.html

SNMP MIB objects that are supported for the SNMP set operation by Junos: https://www.juniper.net/documentation/us/en/software/junos/network-mgmt/topics/topic-map/snmp-mibs-and-traps-supported-by-junos-os.html



Memory Leak Related Issues :

If SNMP response is slow, then verify the memory utilization of the snmpd and mib2d daemons. Take multiple snapshots of the following outputs and see if snmpd or mib2d memory consumption is increasing:

user@router> show system processes extensive | match snmpd 

  PID USERNAME  THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
 1465 root        1  96    0 21480K 18236K select   0:21  0.00% snmpd

user@router> show system processes extensive | match mib2d

  PID USERNAME  THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND    
 1464 root        1  96    0 18720K 10704K select   0:05  0.00% mib2d

If you see that the memory consumption is increasing constantly, then collect the information in the KB22637 - [M, MX, T Routers] Data Collection Checklist [juniper.net] under the 'SNMP' section, and open a case with your technical support representative.

 

Modification History

2026-03-30: Added a note to the solution section

2022-10-03: Updated links.