IPv6 Neighbor Discovery Protocol

Neighbor Discovery Protocol is utilized by IPv6 has for an assortment of undertakings identifying with the neighborhood. What's more, it additionally works with ICMPv6 to finish various operations. The essential assignments for NDP are Router Discovery, Neighbor Discovery and Duplicate Address Discovery. It was contrived for the most part because of the way that IPv6 does not take into account shows and subsequently ARP (Address Resolution Protocol) as utilized with IPv4 is not as a part of operation. 

Router Discovery
In spite of the fact that there is a rendition of DHCP that can be utilized with IPv6, another alternative is to find the local router which can give data identifying with DHCP servers furthermore give a location prefix so that has can arrange their own particular IP Addresses. At the point when a host is initially associated with a connection it consequently multicasts a Router Solicitation message to the All Routers multicast bunch address. Any routers dynamic on the connection will react with a Router Advertisement message to the All Hosts multicast bunch address. The Router Advertisement message can demonstrate an assortment of data. 

Contained inside of the Router Advertisement message is a location prefix or different prefixes identifying with subnets accessible on the local join. The Host then knows which subnet or subnets are nearby and needn't bother with the help of the local router to reach. The Host can naturally arrange it's own IP Address by utilizing the prefix and EUI-64 rules. This includes including an EUI-64 interface identifier got from the interface MAC Address to the publicized prefix. The Interface Identifier part of the IPv6 IP location is utilized to recognize a one of a kind physical interface on a connection. The 48 bit MAC location is isolated into 2 x 3 bytes (24 bits), with the initial 3 bytes know as the OUI (Organizational Unique Identifier), ordinarily known as the Vendor Number. 16 extra bits are embedded between the third and fourth byte, and these bits are spoken to by the Hexadecimal number FFFE. The U/L bit, being the seventh piece in the high request byte is set to an estimation of 1 to show a Global Scope. The procedure of a host naturally arranging it's IP Address from the given prefix is known as Stateless Autoconfiguration. Moreover the Router Advertisement message likewise contains the default jump tally that Hosts ought to utilize. 

Neighbor Discovery 
NDP Hosts can utilize other Solicitation and Advertisement Messages for use with neighboring Hosts, for example, Neighbor Solicitation and Neighbor Advertisement messages: 

Neighbor Solicitation messages can be utilized by Hosts on the LAN to get MAC locations of different Hosts, which is a capacity gave by ARP IPv4. The message is sent to the requested hub multicast address that is connected with a gathering of hosts coordinating the last 6 bits of the location. 

Neighbor Advertisement messages are sent because of Neighbor Solitication messages and contain the Senders IPv6 location and MAC Address. In a few occurrences Hosts can send spontaneous NA messages which would be sent to the All Hosts multicast location of FF02::1. 

Copy Address Detection 
And conveying a Router Solicitation message when joining a connection, a Host likewise conveys a Neighbor Solicitation message for it's own particular IP Address to guarantee no other Host is designed with the same IPv6 address. On the off chance that a Host gets a reaction then it realizes that address can't be utilized and arranges another location. This is like the procedure of Gratuitous ARP, as utilized with IPv4.

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