Completely, 100%, utterly useless to everyone but me:

[hiromasaki]

MRTG Log, MRTG 2.14.7

SNMP Error:
no response received
SNMPv1_Session (remote host: "xxx.xxx.xxx.xxx" [xxx.xxx.xxx.xxx].161)
community: "snmpcomm"
request ID: 1155113307
PDU bufsize: 8000 bytes
timeout: 2s
retries: 5
backoff: 1)
at /usr/share/perl5/SNMP_util.pm line 490
SNMPGET Problem for ifInOctets.2 ifOutOctets.2 sysUptime sysName on snmpcomm@xxx.xxx.xxx.xxx::::::v4only
at /usr/bin/mrtg line 2043
2010-03-10 09:20:01: WARNING: skipping because at least the query for ifInOctets.2 on xxx.xxx.xxx.xxx did not succeed
2010-03-10 09:20:01: WARNING: no data for ifInOctets&ifOutOctets:snmpcomm@xxx.xxx.xxx.xxx. Skipping further queries for Host 192.168.123.254 in this round.
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_2][_IN_] ' $target->[1]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_2][_OUT_] ' $target->[1]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_3][_IN_] ' $target->[2]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_3][_OUT_] ' $target->[2]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_5][_IN_] ' $target->[3]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_5][_OUT_] ' $target->[3]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_8][_IN_] ' $target->[4]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_8][_OUT_] ' $target->[4]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_9][_IN_] ' $target->[5]{$mode} ' did not eval into defined data
2010-03-10 09:20:11: ERROR: Target[xxx.xxx.xxx.xxx_9][_OUT_] ' $target->[5]{$mode} ' did not eval into defined data

Problem: cfgmaker does not "remember" SNMP versions in the generated config file. Watchguard routers do not respond to SNMPv1.
Solution: Hand-edit mrtg.cfg to add :::::2 to the end of all of the appropriate interfaces.