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Background: Know: prereq - ARP, TCP connections depend on address, TCP RST (reset) Recognize:


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Detecting & responding to conflictsEdit

Conflicts usually occur when:
  • An Internet Service Provider (ISP) accidentally assigns two customers the same IP address (either statically or dynamically)[1], if the two customers are assigned the same IP address, one or both of them will disconnect to the Internet.
  • if networks are joined with the existing addresses

Detection of address conflict may be available in case of receiving an ARP packet with sender IP = chosen addr and sender HW that does not equal with ours.

Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks[2], which can convert an IP address into a physical address. A host wishing to obtain a physical address broadcasts an ARP reuqest onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address.
Responses to conflicts:

1. The typical way to treat with conflicts is to simply choosing a different address, but it should be noted that before changing address, we have to be aware that the existing TCP connection has to be reset.

2. Also it is possible to retain the conflicting addresses by not changing the current addresses and resetting the TCP connections and maintaining TCP connections and sending an ARP announcement.

3. In the DHCP console, expand the node for the server you want to work with[3].

References:

[1]: http://compnetworking.about.com/od/workingwithipaddresses/f/ip_conflict.htm

[2]: http://en.wikipedia.org/wiki/Address_Resolution_Protocol

[3]: http://technet.microsoft.com/en-us/magazine/ff606371.aspx