Troubleshooting SNMP

 

Intermapper requires that SNMP be available and configured to display traffic information. The most common cause of not being able to see traffic is that you haven't entered the SNMP Read-only community string. (This is like a password that controls whether another computer can retrieve SNMP information.)

Here are some reasons, sorted from simplest to most complex, why Intermapper might be unable to get SNMP information from a device:

• Wrong DNS name or IP address - (not likely, but we have to mention it)
• No connectivity - Can you ping the device from Intermapper?
• No SNMP agent on the device - Many devices or computers have optional SNMP capabilities that must be installed separately.
• SNMP agent is disabled - Many devices allow you to disable the SNMP capability totally, or from certain ports.
• SNMP agent is based on net-snmp or UCD-snmp package - be sure that the configuration file specifically lists Intermapper's IP address/subnet as an allowed client
• Incorrect OID - especially in custom probes, or in probes that require an OID (See the OID Format How To for details.)
• Wrong Community string - Community strings are case-sensitive. Also, try 'public' (without the quotes) if nothing else is working.
• Intermapper's address is not in the device's access list - Many devices allow access only from certain addresses.
• Firewall blocks a port or traffic on the port - a firewall can block the SNMP port between the Intermapper server and the equipment. Certain firewalls may also block SNMP packets if it suspects that those packets are part of an attack. Intermapper may send and receive all its SNMP queries on the same port and after awhile the firewall may detect this.
• Bugs in a device's SNMP agent - Intermapper uses SNMP Get-Next-Requests in several places. Certain equipment s fails when queried this way.

If you still can't get SNMP information through Intermapper, please contact us. We may have some tricks you can try, or we may learn something!