Why no ARP present in IPv6 network ?

In case of IPv4, router discovery is a combination of ARP, ICMP Router Discovery and ICMP Redirect messages.

In IPv6 network, we don't require all these but Link-Local Address.


1. Link-Local addresses are limited to a physical link.

           Node A(FE80:1::1) --------- (FE80:1::2) Node B (FE80:2::3) --------- (FE80:2::4) Node C

Using this way we can configure automatically link-local address and discover the neighbour.

Eg: If your DHCP server is configured with link-local, your DHCP client will be configured with the same network link-local address. This is called automatic link-local address configuration.

2. To communicate Node A to Node B, it doesn't require a global IPv6 address. So, a link-local address is enough to communicate next-hop through a physical link.

3. User packets will not be forwarded using link-local addresses.

4. All Ipv6 enabled interface, will be automatically configured with a link-local address.

Eg: If you enable IPv6 on any interface and if the interface acts as a client to any dynamic protocol, a link-local address will be configured with the use of the server like DHCP.

Hence, link-local addresses are enough to find the neighbour, and we don't require ARP.

Refer: https://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113328-ipv6-lla.html#:~:text=The%20purpose%20of%20this%20document,local%20address%20in%20a%20network.&text=IPv6%20routers%20must%20not%20forward,a%20link%2Dlocal%20unicast%20address.