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Network Configuration—IPv6inet6 fe80::21c:42ff:fe8d:5dbf%ed0 prefixlen 64 scopeid 0x1inet 192.168.0.225 netmask 0xffffff00 broadcast 192.168.0.255inet6 2a01:3c8::21c:42ff:fe8d:5dbf prefixlen 64 autoconfmedia: Ethernet autoselect (10baseT/UTP)Beside the IPv4 address, there are two IPv6 addresses on the interface. One addressbegins with fe80:: and identified with the scopeid 0x1 tag, which is called alink-local address. Another address begins with 2a01:3c8::, which is the unicastaddress of this interface.The unicast address prefix is obtained from the IPv6 router on the network. Thewhole address is created using the 64 bits Extended Unique Identifier (EUI-64)algorithm, which consists of the hosts MAC address with some minor modifications.The link-local address (that is from the reserved address pool) always starts withfe80:: and is used for local network usage. This can be compared with RFC1819private addresses that are suitable for local use. The network stack will automaticallyassign a link-local address to each IPv6 enabled interface, regardless whether an IPv6router is discovered on the network. This means that in a scenario of a home networkor a lab network, you do not need to run an IPv6 router or have a valid IPv6 prefixin order to establish an IPv6 network. All the hosts will be automatically provisionedwith a link-local address, so they can exchange IPv6 traffic.The network discovery protocol (NDP) helps the host find the router on the networkand then create a unicast address for the interface. NDP is known as the equivalentto ARP protocol in IPv6. The ndp(8) utility is used to control the behavior ofthis protocol:# ndp -aNeighbor Linklayer Address Netif Expire S Flags2a01:3c8:: 0:16:cb:98:d4:bf ed0 20s R R2a01:3c8::21c:42ff:fe8d:5dbf 0:1c:42:8d:5d:bf ed0 permanent Rfe80::216:cbff:fe98:d4bf%ed0 0:16:cb:98:d4:bf ed0 23h58m48s S Rfe80::21c:42ff:fe8d:5dbf%ed0 0:1c:42:8d:5d:bf ed0 permanent Rfe80::1%lo0 (incomplete) lo0 permanent RThe above example shows the discovered IPv6 hosts. The ed0 interface is connectedto an IPv6 enabled network and receives a valid prefix via a router (the first entry ofthe list). The second entry is the unicast address of the ed0. The third and the fourthentries are link-local address for the router and our host. And the last entry belongsto the local host.[ 178 ]