I've noticed an incompatibility with gentoo x86_64 servers running net-snmp and outside monitoring software (particularly opennms). See http://bugs.opennms.org/cgi-bin/bugzilla/show_bug.cgi?id=1316 . Their is a critical fix included in version 5.3.1 of net-snmp but only 5.3.0 is in portage tree and even that I think is still masked for x86_64.
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