Introduction
User has a management tool that works using the SNMP logs from the controller, he can ping the controller using this management tool, but when he sends SNMP requests from the management tool the WLC doesn't reply.
The SNMP server IP address is 192.168.x.y and the WLC's IP address is 10.20.x.y.
He has the following debug taken from the switchport where the WLC is connected.
'debug snmp agent' shows some interesting messages that confirms that the WLC is not sending a packet back.
Cisco Controller) >debug snmp agent enable
(Cisco Controller) >*SNMPTask: Feb 06 14:38:44.616: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 59
*SNMPTask: Feb 06 14:38:44.616: SNMPD: Failed to build in SnmpMessage.
1145 Debug Messages have been dropped*SNMPTask: Feb 06 14:38:44.616: SNMPD: *NOT* sending out packet, out_packet_len = 0
*SNMPTask: Feb 06 14:38:47.621: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 59
*SNMPTask: Feb 06 14:38:47.621: SNMPD: Failed to build in SnmpMessage.
*SNMPTask: Feb 06 14:38:47.621: SNMPD: *NOT* sending out packet, out_packet_len = 0
*SNMPTask: Feb 06 14:38:50.652: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 59
*SNMPTask: Feb 06 14:38:50.652: SNMPD: Failed to build in SnmpMessage.
*SNMPTask: Feb 06 14:38:50.652: SNMPD: *NOT* sending out packet, out_packet_len = 0
*SNMPTask: Feb 06 14:38:53.684: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 50
*SNMPTask: Feb 06 14:38:53.684: SNMPD: Failed to build in SnmpMessage.
*SNMPTask: Feb 06 14:38:53.684: SNMPD: *NOT* sending out packet, out_packet_len = 0
*SNMPTask: Feb 06 14:38:56.715: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 50
*SNMPTask: Feb 06 14:38:56.715: SNMPD: Failed to build in SnmpMessage.
*SNMPTask: Feb 06 14:38:56.715: SNMPD: *NOT* sending out packet, out_packet_len = 0
*SNMPTask: Feb 06 14:38:59.747: SNMPD: Packet from: 192.168.122.11:2509, in_packet_len = 50
*SNMPTask: Feb 06 14:38:59.747: SNMPD: Failed to build in SnmpMessage.
*SNMPTask: Feb 06 14:38:59.747: SNMPD: *NOT* sending out packet, out_packet_len = 0What could be the reason for not responding?
Solution
The management tool needs to be add in the WLC as a "TRAP RECEIVER".
Source
Cisco Wireless LAN Controller Configuration Guide, Release 7.4 - Configuring SNMP
This document is created from the following discussion