When installing Zabbix on Debian 6, you may enconter an error with SNMP checks.
If you get similar output as above you are missing package snmp-mibs-downloader.
set snmp location "Middle of nowhere"
Replace 123.34.56.78 with Firewall’s interface IP which is going to answer the SNMP requests. This command may be omitted – then SNMP will listen on all interfaces.
NMSSNM0075  SNMP v3-Only does not accept community strings.