ARP Commands

Command

ARP -- Display / Edit the ARP table.

Synopsis

ARP ADD <host> <hwtype> <addr>
ARP CMD [0-255]
ARP DROP <host> <hwtype>
ARP [LIST | FLUSH]
ARP MAXQ [0-32767]
ARP LEARN <port | default> [ON | OFF]
ARP PUBLISH <host> <hwtype> <addr>
ARP <TIMEOUT | WAIT> [secs]

Description

The ARP command is used to display and edit the Address Resolution Table, which maps IP addresses to hardware ones.

<host>   is an IP address in dotted quad form.
<hwtype> is the hardware type, i.e. "ax25" "netrom" or "ether".
<addr>   is the hardware address (callsign / ethernet addr).

ARP by itself, lists the table.
ARP ADD is used to add an entry to the table.
ARP CMD specifies the functionality of the ARP command.
ARP DROP is used to delete an entry from the table.
ARP FLUSH flushes temporary entries from the table.
ARP LEARN controls arp learning.
ARP LIST lists the table.
ARP MAXQ limits no. of datagrams queued pending resolution.
ARP PUBLISH adds an ARP proxy entry for a hidden system.
ARP TIMEOUT specifies max life of a dynamic entry (secs).
ARP WAIT specifies how many secs to wait for an ARP reply.

Examples

ARP ADD 44.131.91.2 ax25 gb7pzt-5    Add ax25 entry
ARP DROP 44.131.91.7 ax25            Delete ax25 entry
ARP PUB 44.131.91.127 ax25 g8pzt     Publish 91.127
ARP TIMEOUT 30                       Set 30 sec lifetime
ARP LEARN 2 ON                       Enable learn on port 2
ARP LIST                             List the table
ARP                                  List the table

More Info

ARP PUBLISH is used when a host is "hidden" on a network which is only accessible via XRPi, and allows XRPi to respond to ARP requests for the hidden system, by returning its own hardware address.

The flags for "ARP CMD" are as follows:

	1 = Command is available to secure sysops
	2 = Command is available to non-secure sysops
	4 = Command is available to users
	8 = Private addr's visible to secure sysops
	16 = Private addr's visible to non-secure sysops
	32 = Private addresses visible to all users

The default is 255 (all options enabled).
A "secure sysop" is at the console, or on a private LAN.
A "non-secure sysop" is one accessing via a public RF network.

ARP LEARN controls whether or not XRPi "learns" ARP info from passing ARP traffic. The default is for learning to be ON, but it may be enabled/disabled using ARP LEARN DEFAULT [on | off]. Regardless of the default setting, learning can be enabled or disabled for any port, using ARP LEARN <portnum> [on | off]. if not refreshed, learned entries persist for the interval specified by TIMEOUT, usually 15 minutes.

ARP FLUSH removes temporary entries, i.e. those pending resolution. The default lifetime for these entries is specified by ARP WAIT (default 30 secs).

ARP MAXQ [0-32767] is used to limit the no. of datagrams which may be queued pending resolution. The default is 100. If the address fails to resolve, the queued datagrams are dropped.

Availability

The LIST subcommand is available to everyone, but the remainder are sysop-only.

Files

ARP commands to be executed at boot-up are usually placed in IPROUTE.SYS, but they may also be used in BOOTCMDS.SYS.

Notes

In order for this command to have any meaning, the router must have an IP address and be connected to an IP-capable network.

You cannot add hardware address types for which there is no compatible interface, e.g. an attempt to add an Ethernet address on a system with no Ethernet interfaces will fail.

The defaults are as follows:

TIMEOUT 900 secs. WAIT 30 secs, MAXQ 100

See Also

IPROUTE.SYS -- IP Routing / Configuration File
ARP(5) -- Address Resolution Protocol.
BOOTCMDS.SYS -- Boot-up commands file.