05-06-2002
ARP does not take care of address uniqueness. That's not arp's job. It assumes the addresses are unique and will fail if they are not.
Your second question does not compute for me. I would assume that you are running slip or ppp or something like that. If you really have a mutant ISP that is assigning you a MAC address, you need to determine which type of mac address it is. If it's a ethernet address, your ISP could apply for a block of ethernet addresses. The ethernet address has two parts: a manufacturer id and unique address within the manufacturer id. Other lans work the same way.
To support their switchover product, HP would give out ethernet addresses not assigned to any hardware. All of HP's addresses are unique to HP. And it's up to HP to make sure that they don't give out the same address twice.
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arp(1M) System Administration Commands arp(1M)
NAME
arp - address resolution display and control
SYNOPSIS
arp hostname
arp -a [-n]
arp -d hostname
arp -f filename
arp -s hostname ether_address [temp] [pub] [trail]
DESCRIPTION
The arp program displays and modifies the Internet-to-MAC address translation tables used by the address resolution protocol (see arp(7P)).
With no flags, the program displays the current ARP entry for hostname. The host may be specified by name or by number, using Internet dot
notation.
OPTIONS
-a Display all of the current ARP entries. The definition for the flags in the table are:
M Mapping; only used for the multicast entry for 224.0.0.0
P Publish; includes IP address for the machine and the addresses that have explicitly been added by the -s option. ARP will
respond to ARP requests for this address.
S Static; not learned for the ARP protocol.
U Unresolved; waiting for ARP response.
You can use the -n option with the -a option to disable the automatic numeric IP address-to-name translation. Use arp -an or arp
-na to display numeric IP addresses.
-d Delete an entry for the host called hostname. This option may only be used by the super-user.
-f Read the file named filename and set multiple entries in the ARP tables. Entries in the file should be of the form:
hostname MACaddress [temp] [pub] [trail]
See the -s option for argument definitions.
-s Create an ARP entry for the host called hostname with the MAC address MACaddress. For example, an Ethernet address is given as
six hexadecimal bytes separated by colons. The entry will be permanent unless the word temp is given in the command. If the word
pub is given, the entry will be published. For instance, this system will respond to ARP requests for hostname even though the
hostname is not its own. The word trail indicates that trailer encapsulations may be sent to this host. arp -s can be used for a
limited form of proxy ARP when a host on one of the directly attached networks is not physically present on the subnet. Another
machine can then be configured to respond to ARP requests using arp -s. This is useful in certain SLIP configurations.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO
ifconfig(1M), arp(7P), attributes(5)
SunOS 5.10 7 Mar 2003 arp(1M)