Alright I found it! Here is the deal. snmpwalk has an undocumented switch, -T. The -T switch is deprecated and points us to use the host form protocol:hostname . This means that TCP:my.server.net actually uses the snmp over tcp. This warning from the -T switch seems to be the only place the TCP:my.server.net host form is documented. Oh well, at least I know it now. =)

Since I don't have any problem with qx()'ing snmpwalk and parsing the output, this will do just fine.

--habit