SNMP-based Extensions Troubleshooting Guide

[GiuseppeRanieri]

• Summary
• Things to know
• Where to look for symptoms
• Problems
• SNMP always times out
• Custom interval logic
• SNMP DS restarted by ECC - CPU/ MEM exceeding
• Blocked fragmented IP/UDP packets in the network
• Fastcheck failed with an authentication error
• DEVICE_CONNECTION_ERROR
• Timeouts always - invalid privacy protocol
• Overflow of 32-bit counters
• Timeout on 32-bit or 64-bit specific counters
• What's next

Summary

This troubleshooting article will help resolve some common issues faced while installing and setting up SNMP-based extensions.

 

Things to know

Where to look for symptoms

Specific symptoms mentioned in this article can be seen in the Extensions app and file logs. Here is how you can find them.

SFM logs

SFM logs are available in the health tab on the Extension page in the Extensions app

• Log files can be found in paths:
  • Linux: /var/lib/dynatrace/remotepluginmodule/log/extension/datasources/<directory_corresponding_to_the_used_extension>
  • Windows: %PROGRAMDATA%/dynatrace/remotepluginmodule/log/extensions/datasources/<directory_corresponding_to_the_used_extension>

TCPdump

TCPdump collection steps

• Record communication from the ActiveGate, including traffic from the interface connected to the SNMP device, file format .cap
• Use the command below or https://www.wireshark.org/
  

  tcpdump -i \<interface\> -w \<output file\>​

  Example: 
  

  tcpdump -i eth0 -w output.cap​

Problems

SNMP always times out

Symptoms

• SNMP always times out on 1.3.6.1.2.1.1.5.0
• Changing timeout/ max retries/ max OIDs per query doesn't help
• SNMPwalk & SNMPget by Dynatrace don't work
• Querying by Third-party tools work

Troubleshooting

1.  Re-check passwords/ community string
   1. if they're copied, enter them manually (while copying, some white characters can be copied by mistake)
   2. if they have special characters (@ $ # % etc.) you might need to escape them with \ character, depending on your network device
   3. if these changes don't help to exclude problems with secrets, change the password to something simple like "12345678" and try once again
2. Gather tcpdump ( tcpdump -w res.pcap) and look inside if there is visible request from AG to endpoint provided in config and if there is response:
   1. Yes
      Look for the IP address, from which device is it responding, if it's different – SNMP data source  won't recognize it. To confirm the issue, run SNMPwalk with below flag:
      

      ./dynatracesourcesnmp --snmpwalk --ip $DEVICE_IP --oid $OID -v SNMPv2c -c $COMMUNITY_STRING -t 10 --unconnected-udp​

      This command runs a performance health check, which runs a one-round query with all selected feature sets as separate queries. The result prints many useful pieces of information per single request. Such as response time, oids queried, oids returned and oids fetched. 
      

      
      This behavior can mean 2 things:

      • The device is configured to respond to a different interface; this should be reconfigured on the device itself
      • There is some device in the middle between the ActiveGate and the device that changes the IP source for SNMP query responses
   2. No
      Traffic is not reaching AG. This is most likely related to network problems.

Custom interval logic

Symptoms

• Data gaps in intervals longer than the interval declared in the extension (for example, every 3 minutes instead of 1 minute)
• dsfm:extension.status not showing any error
• dsfm:datasource.snmp.query.timemetric shows exceeded query time
• Datasource log: [ds:snmp] [info] [OK] TEST.COMPANY.COM SNMP query time exceeded: 1m41.212683135s, 2m9.964s, TEST.COMPANY.COM CpuTime: 925ms, MemRss: 561345

Solution

The defined interval needs to be changed. This can be done in 2 ways.

1. Change the interval for specific extensions by modifying the extension.yaml. Check how to do it in the documentation: Extension YAML file — Dynatrace Docs
2. Use the Custom Extensions Creator app to update this. The screenshot below shows where this field is available.

SNMP DS restarted by ECC - CPU/ MEM exceeding

Symptoms

• "HIGH_CPU" or "HIGH_MEMORY" logs status can be found in the snmp_statuses.log. DS hits the limits imposed by ECC
• dsfm:extension.engine.status with dt.extension.status dimension set to HIGH_CPU_RESTART (or HIGH_MEMORY_RESTART) is sent
  

Solution

• If you don't need to collect all metrics from the extension, turn off some feature sets in the activation monitoring configuration
• Set dedicated performance profile configuration (https://docs.dynatrace.com/docs/extend-dynatrace/extensions20/dedicated-performance-profile)

Blocked fragmented IP/UDP packets in the network

Symptoms 

code 38 - DEVICE_CONNECTION_ERROR always with the same OID.
The error should be visible in SFM logs and file logs.

Solution

Decrease the advanced options parameter MaxRepetitions (size of response from f5), and if needed MaxOidsPerQuery (size of request)

Note:

• this solution may lead to higher CPU and memory usage.
• Low values of MaxRepetitions and MaxOidsPerQuery are not optimal, and cause that data source to need more time to request OIDs from the device

Fastcheck failed with an authentication error                            

Symptoms

AUTHENTICATION_ERROR with one of the messages: wrong digest for user, unsupported security level, unknown username

Troubleshooting

1. wrong digest for user
   1. Double check the password is correct
      1. if copied, write them manually (while copying, some white characters can be copied by mistake)
      2. if the password has special characters (@ $ # % etc.), try removing them
      3. if these changes don't help to exclude problems with secrets, change the password to something simple like "12345678" and try once again
   2. Select correct authentication protocol (MD5, SHA, ...) in the Extension configuration
2. unsupported security level
   1. Select the correct Security Level (authPriv, authNoPriv, noAuthNoPriv) in the Extension configuration
3. unknown username
   1. Double check the user is correct in the Extension configuration

DEVICE_CONNECTION_ERROR

Symptom 

Device logs are showing DEVICE_CONNECTION_ERROR, but the SNMP object of the call works

Solution

1. With a tcpdump you'll have a complete overview of the traffic from the ActiveGate. Set it up based on the instructions above.
2. Search the host in the file produced by the tcpdump collection. If the IP is different, it is because that it comes from a different interface device. Dynatrace data source does not support such a configuration.
3. Since ActiveGate version 289+, we can check, with our binary, if a response is received, it confirms that the issue mentioned earlier is indeed the cause. In that case, the device should be reconfigured to ensure it responds on the same interface from which it receives requests. This is usually addressed by a network admin.

Timeouts always - invalid privacy protocol

Symptom

DEVICE_CONNECTION_ERROR - Timeout

Solution

Select the correct Privacy Protocol (AES, DES, ...) in the Extension configuration

Overflow of 32-bit counters

Symptom

Invalid values reported for Interface incoming traffic / Octets received / ifInOctets / 1.3.6.1.2.1.2.2.1.10 or Interface outgoing traffic / Octets transmitted / ifOutOctets / 1.3.6.1.2.1.2.2.1.16

Solution

Use high 64-bit capacity counters - enable Interfaces 64-bit feature set (disable Interfaces 32-bit)

Timeout on 32-bit or 64-bit specific counters

Standard 32-bit capacity traffic counters or high 64-bit capacity traffic counters are not supported in the device

Symptom

Timeout always seen on 1.3.6.1.2.1.2.2.1.10 or 1.3.6.1.2.1.2.2.1.16 or 1.3.6.1.2.1.31.1.1.1.6 or 1.3.6.1.2.1.31.1.1.1.10

Solution

Query the device using SNMPwalk for problematic OID to confirm that the OID is not available, then disable Interfaces 32-bit or Interfaces 64-bit accordingly, or reconfigure your device so OID is available

What's next

Please reach out to support if this article does not help. In the support ticket, please provide:

• Support Archive. How to collect a Support Archive
• Result of SNMPbulkwalk command for the OIDs not working
• tcpdump
• a link to this article and the outcome of the troubleshooting steps.

If this article has helped you and provided you with valuable insight, please give it a thumbs-up (kudos).

[AntonPineiro]

Thank you! 

[AntonioSousa]

Very good Guide!