While testing out the latest net-snmp bits, I noticed that various TCP and UDP mibII OIDs would continuosly display zeros on my Solaris 10 update 6 host:
$ snmpwalk -c ... -v 2c localhost udpInDatagrams.0
UDP-MIB::udpInDatagrams.0 = Counter32: 0
Generate lots of UDP traffic.
$ snmpwalk -c ... -v 2c localhost udpInDatagrams.0
UDP-MIB::udpInDatagrams.0 = Counter32: 0
This turns out to be caused by a net-snmp bug, which is fixed by applying the patch attached to the bug report. I am posting this here to help others who may bump into this issue.