Browse Prior Art Database

Duplicate Internet Protocol Address Detection Based on Gratuitous Address Resolution Protocol

IP.com Disclosure Number: IPCOM000122962D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 136K

Publishing Venue

IBM

Related People

Jou, T: AUTHOR

Abstract

Disclosed is a protocol that can prevent a newly configured host from making any damage to the host that has been the owner of the same Internet Protocol (IP) address. The solution is based on the de-facto gratuitous Address Resolution Protocol (ARP) packet plus modification on processing of this packet.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Duplicate Internet Protocol Address Detection Based on Gratuitous
Address Resolution Protocol

      Disclosed is a protocol that can prevent a newly configured
host from making any damage to the host that has been the owner of
the same Internet Protocol (IP) address.  The solution is based on
the de-facto gratuitous Address Resolution Protocol (ARP) packet plus
modification on processing of this packet.

      The ARP defines the way to resolve the hardware address of a
host on a broadcast network based on the target host's IP address.
The hardware address is always unique for each hardware module, but
no guarantee on the uniqueness of IP addresses.  With current trend
of connecting each host to a network, there is an increasing chance
that the same IP address is used on different hosts due to users' or
network administrators' mistake, or an error from an IP address
assigning program such as a BOOTP or DHCP server.  This memo is to
define an extension to the original protocol to prevent a newly
configured host from making any damage to the host that has been the
owner of the same  IP address.  The solution is based on the de-facto
gratuitous ARP packet  plus modification on processing of this
packet.

      The ARP is used to determine a host's IP address based on its
network address.  To adapt to the possible changes of the association
between a hardware address and an IP address, two mechanisms are
described in the protocol:
  o  When a host receives an ARP packet and the sender's IP
      address exists in its ARP table, the host should update
      the cached ARP entry with the sender's hardware address
      in the packet.
  o  Each host ages away old ARP entries to allow changes on
      the network.

      With the popularity of today's internet activities, more
and more hosts are connected to networks and have IP addresses
assigned.  There is an increasing chance of the same IP address being
used on two different hosts due to any kind of error.  If this ever
happens, neither of the the two hosts can reliably communicate to
others because the unpredictable hardware address resolution on this
shared IP address.  This is especially a serious threat to a server
that many  clients depend on.

The problem can be avoided gracefully if all following conditions are
achieved:
  1.  The second host that tries to use the same IP address
       detects another host is using this address, and turns
       down its interface.
  2.  The host that originally owns the IP address notifies
       the the second host for the duplication and then can
       keep operating.
  3.  All other hosts on the network are not confused by the
       second host's attempt.

      A host running one of many recent Transmission Control
Protocol/Internet Protocol (TCP/IP) implementations can generate a
gratuitous ARP request packet when any of its interfaces is
configured, usually...