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Full Discussion: What arp -s is good for
The Lounge War Stories What arp -s is good for Post 302719647 by Corona688 on Monday 22nd of October 2012 07:11:36 PM
Old 10-22-2012
What arp -s is good for

A customer appears to have drastically misunderstood our instructions for connecting to our WAN. He set his PC IP address to the same as one of the bridges. Smilie Smilie This caused much confusion on the network, to put it mildly. He called to complain about the poor performance of the network he ruined, then made himself unavailable for phone calls so it couldn't be fixed.

Even blocking his MAC address didn't help. The bridging problem happens in midair, nowhere the server can control. If I could at least get into the bridge, I could reconfigure it to a different IP and allow traffic again...

So, on the server, I tried this:

Code:
arp -d 192.168.6.101 ; arp -s 192.168.6.101 00:60:b3:07:0e:8e

This succeeded in forcing the server to talk to the bridge, not to him. I was then able to get into the bridge's web interface and change its IP from there. From there it was easy.
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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)
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