In case of SNMP logging to a remote node, the log destination should be set to SNMP destination. Allocation de-allocation of each port block triggers sending a SNMP trap message to the trap destination.
*A:left-a20>config>log# info
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filter 1
default-action drop
entry 1
action forward
match
application eq "nat"
number eq 2012
exit
exit
exit
snmp-trap-group 6
trap-target "nat" address 192.168.1.10 port 9001 snmpv2c notify-community "private"
exit
log-id 6
filter 1
from main
to snmp
exit