ZyXEL Communications P-334WT Support Notes page 143

If the machine coldstarts, the trap will be sent after booting.
2. warmStart (defined in RFC-1215) :
If the machine warmstarts, the trap will be sent after booting.
3. linkDown (defined in RFC-1215) :
If any link of IDSL or WAN is down, the trap will be sent with the port number . The port
number is its interface index under the interface group.
4. linkUp (defined in RFC-1215) :
If any link of IDSL or WAN is up, the trap will be sent with the port number . The port number is
its interface index under the interface group.
5. authenticationFailure (defined in RFC-1215) :
When receiving any SNMP get or set requirement with wrong community, this trap is sent
to the manager.
6. whyReboot (defined in ZYXEL-MIB) :
When the system is going to restart (warmstart), the trap will be sent with the reason of
restart before rebooting.
(i) For intentional reboot :
In some cases (download new files, CI command "sys reboot", ...), reboot is done
intentionally. And traps with the message "System reboot by user !" will be sent.
(ii) For fatal error :
System has to reboot for some fatal errors. And traps with the message of the fatal code
will be sent.