I've received numerous requests for information on
which network switch/router systems implement SNMPv3,
though my own request was for information on operational
deployments of SNMPv3 in networks.
Folks interested in an *incomplete* list of implementations
with SNMPv3 might want to look at:
A number of network equipment vendors have shipped SNMPv3,
but are NOT included from that list. So if SNMPv3 is something
you are interested in, ask your vendors directly for more information.
Of particular interest is the existence of at least one
freely distributable implementation "NetSNMP" (formerly UC Davis
SNMP). This works out of the box on most modern UNIX systems,
meaning that one can use SNMPv3 on UNIX servers even if the OS
vendor didn't include it directly. For more on that implementation,
browse the above URL.