This object indicates the reason for logging this ARP flow.
'unknown' indicates unknown reason.
'deny' indicates that this ARP flow is logged because it is
denied by Dynamic ARP Inspection feature.
'aclDeny' indicates that this ARP flow is logged because it is
denied by a configured ARP ACL.
'aclPermit' indicates that this ARP flow is logged because it
is permitted by a configured ARP ACL.
'dhcpDeny' indicates that this ARP flow is logged because it
is denied when comparing with DHCP bindings information.
'dhcpPermit' indicates that this ARP flow is logged because
it is permitted when comparing with DHCP binding information.
'probePermit' indicates that this ARP flow is logged because
it is a permitted ARP-Probe flow.