Posts
- Each IPv6 host including routers uses an additional unicast address called a Link-local address.
- Link-Local addresses are used for some overhead protocols that stay local to one subnet but not for transferring data. eg., NDP (Neigbour Discovery protocol) which is the same as IPv4's ARP.
- Also, Routers use link-local addresses as the next-hop IP address in IPv6 routes.
- IPv6 hosts use Link-local addresses of the router(in the same subnet) as the default gateway address.
- Link-local addresses are unicast addresses, not multicast.
- Routers do not route packets with the link-local destination address.
- Every IPv6 host interface (and router interface) can create its own link-local address automatically, solving some initialization problems in hosts.
How Routers create Link-local addresses?
- IOS can create automatically or it can be configured using the command - IPv6 address FE80::1 link-local
- All Link-local addresses start with the same prefix FE80::/10
First 10 Bits -------- FE80::/10
Next 54 Bits -------- binary 0's
- IOS create Link-local address automatically in the below format:
- Cisco routers use the EUI-64 format to create the interface ID, but other OS's randomly create the interface ID.
- IOS creates a link-local address for any interface that has configured at least one other unicast address (Global unicast or Unique local) using IPv6 address command. Even IPv6 enable interface subcommand causes the router to create a Link-local address.
- Two routers in the same link can forward packets between each other using Link-local address.
Comments