Editing ICMP Router Discovery Protocol

{{Short description|Protocol to discover routers}}
In [[computer networking]], the '''ICMP Internet Router Discovery Protocol''' ('''IRDP'''), also called the '''Internet Router Discovery Protocol''',<ref name="etut">{{cite web|title=IRDP|url=http://etutorials.org/Networking/Integrated+cisco+and+unix+network+architectures/Chapter+12.+Designing+for+High+Availability/IRDP/|website=etutorials.org|accessdate=23 June 2016}}</ref> is a protocol for computer hosts to discover the presence and location of [[router (computing)|router]]s on their [[IPv4]] [[local area network]]. Router discovery is useful for accessing computer systems on other nonlocal area networks.<ref name="Juniper">{{cite web|title=ICMP Router Discovery Overview|url=http://www.juniper.net/documentation/en_US/junos14.2/information-products/pathway-pages/config-guide-routing/config-guide-routing-icmp.html|website=www.juniper.net|publisher=Juniper Networks|accessdate=23 June 2016}}</ref> The IRDP is defined by the IETF RFC 1256 standard,<ref name="Javvin">{{cite book|title=Network Protocols Handbook|date=2005|publisher=Javvin Technologies Inc.|isbn=9780974094526|page=69|url=https://books.google.com/books?id=D_GrQa2ZcLwC&q=%22ICMP+Router+Discovery%22&pg=PA69|accessdate=23 June 2016|language=en}}</ref> with the [[Internet Control Message Protocol]] (ICMP) upon which it is based defined in IETF RFC 792. IRDP eliminates the need to manually configure routing information.<ref name="etut" />

== Router discovery messages ==

To enable router discovery, the IRDP defines two kinds of ICMP messages:<ref name="Carrell">{{cite book|last1=Carrell|first1=Jeffrey L.|last2=Chappell|first2=Laura|last3=Tittel|first3=Ed|last4=Pyles|first4=James|title=Guide to TCP/IP|date=2013|publisher=Cengage Learning|isbn=978-1133019862|pages=288–289|url=https://books.google.com/books?id=mFr7CAAAQBAJ&q=%22Router+Discovery%22&pg=PA299|accessdate=23 June 2016|language=en}}</ref><ref name="Chen">{{cite book|last1=Chen|first1=Jyh-Cheng|last2=Zhang|first2=Tao|title=IP-Based Next-Generation Wireless Networks: Systems, Architectures, and Protocols|date=17 February 2004|publisher=John Wiley & Sons|isbn=9780471478263|page=182|url=https://books.google.com/books?id=2kSjPFW4tqEC&q=%22Router+Discovery%22&pg=PA182|accessdate=23 June 2016|language=en}}</ref>

* The ICMP Router Solicitation message is sent from a computer host to any routers on the local area network to request that they advertise their presence on the network.
* The ICMP Router Advertisement message is sent by a router on the local area network to announce its IP address as available for routing.

When a host boots up, it sends solicitation messages to IP multicast address 224.0.0.2.<ref name="Carrell" /> In response, one or more routers may send advertisement messages. If there is more than one router, the host usually picks the first message it gets and adds that router to its [[routing table]]. Independently of a solicitation, a router may periodically send out advertisement messages.<ref name="Panwar">{{cite book|last1=Panwar|first1=Shivendra S.|title=TCP/IP Essentials: A Lab-Based Approach|date=2004|publisher=Cambridge University Press|isbn=9780521601245|page=81|url=https://books.google.com/books?id=NbYKmCfw_PsC&q=%22ICMP+Router+Discovery%22&pg=PA81|language=en}}</ref> These messages are not considered a routing protocol, as they do not determine a routing path, just the presence of possible gateways.<ref name="Javvin" />

== Extensions ==

The IRDP strategy has been used in the development of the [[IPv6]] neighbor discovery protocol.<ref>{{cite web|title=Supported ICMP Router Discovery and IPv6 Neighbor Discovery Standards|url=http://www.juniper.net/documentation/en_US/junos15.1/topics/reference/standards/icmp-neighbor-discovery.html|website=juniper.net|publisher=Juniper Networks|accessdate=23 June 2016}}</ref> These use [[ICMPv6]] messages, the IPv6 analog of ICMP messages. Neighbor discovery is governed by IETF standards RFC 4861 and RFC 4862.

IRDP plays an essential role in mobile networking through IETF standard RFC 3344.<ref name="etut" /> This is called [[MIPv4]] ''Agent discovery''.<ref name="Chen" />

==See also==
* [[Dynamic Host Configuration Protocol]]

== References ==

<references />

== External links ==
* {{IETF RFC|1256|link=no}}: ICMP Router Discovery Messages

[[Category:Internet Standards]]
[[Category:Internet protocols]]