Figure 300 Backup Gateway - ZyXEL Communications P-662H-61 User Manual

Appendix J Command Interpreter
updates its ARP table. This way the ZyXEL Device has a correct gateway ARP entry to
forward packets through the backup gateway. If ackGratuitous is off or not set to force
updates, the ZyXEL Device will not update the gateway ARP entry and cannot forward
packets through gateway B.

Figure 300 Backup Gateway

Updating the ARP entries could increase the danger of spoofing attacks. It is only
recommended that you turn on ackGratuitous and force update if you need it like in the
previous backup gateway example. Turning on the force updates option is more dangerous
than leaving it off because the ZyXEL Device updates the ARP table even when there is an
existing entry.
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P-662H/HW-D Series User's Guide