ZyXEL Communications 4.04 User Manual
Chapter 15 IP Commands
ZyWALL (ZyNOS) CLI Reference Guide
98
15.1.2 ARP Commands
The following section lists the ARP commands.
15.1.3 ARP Behavior and the ARP ackGratuitous Command Details
The ZyWALL does not accept ARP reply information if the ZyWALL did not send out a
corresponding request. This helps prevent the ZyWALL from updating its ARP table with an
incorrect IP address to MAC address mapping due to a spoofed ARP. An incorrect IP to MAC
address mapping in the ZyWALL’s ARP table could cause the ZyWALL to send packets to
the wrong device.
corresponding request. This helps prevent the ZyWALL from updating its ARP table with an
incorrect IP address to MAC address mapping due to a spoofed ARP. An incorrect IP to MAC
address mapping in the ZyWALL’s ARP table could cause the ZyWALL to send packets to
the wrong device.
15.1.3.1 Commands for Using or Ignoring Gratuitous ARP Requests
A gratuitous ARP request is an ARP request that a host sends to resolve its own IP address.
The packet uses the host’s own IP address as the source and destination IP address. The packet
uses the Ethernet broadcast address (FF:FF:FF:FF:FF:FF) as the destination MAC address.
This is used to determine if any other hosts on the network are using the same IP address as the
sending host. The other hosts in the network can also update their ARP table IP address to
MAC address mappings with this host’s MAC address.
The packet uses the host’s own IP address as the source and destination IP address. The packet
uses the Ethernet broadcast address (FF:FF:FF:FF:FF:FF) as the destination MAC address.
This is used to determine if any other hosts on the network are using the same IP address as the
sending host. The other hosts in the network can also update their ARP table IP address to
MAC address mappings with this host’s MAC address.
The
ip arp ackGratuitous
commands set how the ZyWALL handles gratuitous ARP
requests.
• Use
ip arp ackGratuitous active no
to have the ZyWALL ignore gratuitous ARP
requests.
• Use
ip arp ackGratuitous active yes
to have the ZyWALL respond to gratuitous
ARP requests.
Table 43 ARP Commands
COMMAND
DESCRIPTION
M
ip arp ackGratuitous active
[yes|no]
Turns the acceptance of gratuitous ARP (Address Resolution
Protocol) packets on or off. See
Protocol) packets on or off. See
for
details.
R+B
ip arp ackGratuitous forceUpdate
[on|off]
Has the ZyWALL update an existing ARP entry for which a
gratuitous request was received. See
gratuitous request was received. See
for details.
R+B
ip arp add <ip-address> ether
<mac-address>
Adds ARP information.
R+B
ip arp attpret <on|off>
Allows or disallows ZyWALL to receive ARP from a different
network or not.
network or not.
R+B
ip arp force <on|off>
Enables or disables the ARP timeout function.
R+B
ip arp gratuitous <on|off>
Turns duplicate IP address detection (based on gratuitous
ARPs) on or off.
ARPs) on or off.
R+B
ip arp status <interface>
Displays an interface’s ARP status.
R+B
ip arp reqUpdateTable <on|off>
Sets whether or not the ZyWALL updates its ARP table based
on the source IP address and MAC address of received ARP
request packets. This is off by default. If you turn this on, the
setting changes back to off when the ZyWALL restarts.
on the source IP address and MAC address of received ARP
request packets. This is off by default. If you turn this on, the
setting changes back to off when the ZyWALL restarts.
R+B