HP-UX 11.31: net-snmp no longer works after recent patches

[Chris Howard]

We had configured net-snmp and had it working OK.

Over this past weekend we applied a package of suggested patches.

Now net-snmp is not working.

The error message is

Error opening specified endpoint "udp:W.X.Y.Z:161"

Changing to "tcp:W.X.Y.Z:161" in the config file gets it running again, and it shows up on both tcp and udp port 161

We are running as root.  I don't see any other processes on the 161 port.

What's up with the udp/tcp issue?

[Matti_Kurkela]

How are you checking the port?

Since SNMP normally runs on top of UDP, it won't look like the usual TCP listener.

This is how the standard OpenView SNMP agent of HP-UX looks like in netstat output:

# netstat -anf inet |grep 161
udp        0      0  *.161                  *.*   

Note that there is no "LISTEN" keyword in the rightmost column.

Using the lsof command, it might be easier to find the process:

# lsof -i udp:161
COMMAND  PID USER   FD   TYPE     DEVICE SIZE/OFF NODE NAME
snmpdm  1457 root    6u  IPv4 0x43959900      0t0  UDP *:snmp (Idle)

Depending on exactly how you've stopped the HP-UX standard SNMP agent, it is possible that patching might have replaced the file you had modified to replace the standard agent with net-snmp and thus caused the standard agent to activate again, grabbing the UDP/161 port for itself.

If /etc/rc.config.d/SnmpMaster file contains setting SNMP_MASTER_START=1, or if the setting does not exist at all, the standard agent will start at boot.