Chapter 15 IP Commands
15.1.2 ARP Commands
The following section lists the ARP commands.
Table 43 ARP Commands
COMMAND | DESCRIPTION | M |
ip arp ackGratuitous active | Turns the acceptance of gratuitous ARP (Address Resolution | R+B |
[yesno] | Protocol) packets on or off. See Section 15.1.3 on page 98 for |
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| details. |
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ip arp ackGratuitous forceUpdate | Has the ZyWALL update an existing ARP entry for which a | R+B |
[onoff] | gratuitous request was received. See Section 15.1.3 on page |
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| 98 for details. |
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ip arp add | Adds ARP information. | R+B |
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ip arp attpret <onoff> | Allows or disallows ZyWALL to receive ARP from a different | R+B |
| network or not. |
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ip arp force <onoff> | Enables or disables the ARP timeout function. | R+B |
ip arp gratuitous <onoff> | Turns duplicate IP address detection (based on gratuitous | R+B |
| ARPs) on or off. |
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ip arp status <interface> | Displays an interface’s ARP status. | R+B |
ip arp reqUpdateTable <onoff> | Sets whether or not the ZyWALL updates its ARP table based | R+B |
| on the source IP address and MAC address of received ARP |
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| request packets. This is off by default. If you turn this on, the |
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| setting changes back to off when the ZyWALL restarts. |
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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.
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 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.
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ZyWALL (ZyNOS) CLI Reference Guide |
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