Link-Local IPv6 Address
|IPv6 Address Type:||Link-Local|
|IPv4 Equivalent:||169.254.0.0/16 Link-Local|
These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN.
They do not need to be unique outside of that link.
Link-local addresses may appear as the source or destination of an IPv6 packet.
Routers must not forward IPv6 packets if the source or destination contains a link-local address.
IPv6 Link-Local Addresses
Link-Local Addresses are used by Nodes to communicate to other Nodes on the same Link. Link-Local addresses are not Routeable.
IPv6#<input>sh ipv6 int fa0/0</input> FastEthernet0/0 is up, line protocol is up IPv6 is enabled, <notice>link-local address is FE80::21B:D4FF:FE0F:8CA2</notice> No Virtual link-local address(es): Description: Outside: Internet connection to ISP Global unicast address(es): 2001:16D8:DD85:146::2, subnet is 2001:16D8:DD85:146::/64 Joined group address(es): FF02::1 FF02::2 FF02::D FF02::16 FF02::1:FF00:2 FF02::1:FF0F:8CA2 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds Hosts use stateless autoconfig for addresses.
Example why originating interface is important
Notice in the example below, we telnet to the Heimdal Router - the very same we're on - even I know that the Link-Local address FE80::218:18FF:FE7C:B440 is on a neighboring Router called Campus1.
<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440</input> Trying FE80::218:18FF:FE7C:B440 ... Open !!!Netadmin Please upgrade the network security!!! banner motd User Access Verification Password: <notice>Heimdal</notice>><input>exit</input> [Connection to FE80::218:18FF:FE7C:B440 closed by foreign host]
Link-Local addresses are local on a link. We need to tell on which interface the Link-Address are on. First we need to find the interface on which the address resides.
Heimdal#<input>show ipv6 neighbor | inc B440</input> FE80::218:18FF:FE7C:B440 0 0018.187c.b440 STALE <notice>Vl1</notice>
In the output in previous command, it's seen that the Link-Local address lives in Vlan1. Now we telnet from that source-interface - and Voila everything works as expected.
<notice>Heimdal</notice>#<input>telnet FE80::218:18FF:FE7C:B440 /source-interface vlan1</input> Trying FE80::218:18FF:FE7C:B440 ... Open !!!Netadmin please upgrade Network Security!!! banner motd User Access Verification Password: <notice>Campus1</notice>>