As discussed by Teare (2010), one of the major changes introduced in
OSPFv3 is that
the protocol’s header has been redesigned. The header is no longer
complex as compared to the header in OSPFv2. The header now includes an
instance ID field. Routing in IPv6 is done on a per–interface basis not on
per–subnet. Each IPv6 routing protocol is more concerned 16 about the link on
which it is configured but not the subnet. The addition of the new instance ID
field to the protocol structure therefore makes it possible for several OSPFv3
instances or addresses to be enabled on the same link. By default, instance ID
is 0. When there is an additional instance, it is increased. Each OSPF instance
is assigned a separate instance ID.
Also, instance ID has local link significance only. This means that
before OSPFv3 routers can become neighbors, they must have identical instance
IDs. For example, if a router receives a packet whose instance ID is not the
same as its own instance ID, it simply discards the packet.
Additionally, because the OSPFv3 header has been redesigned its hello
structure has also been changed (Coltun et al, 2008). As discussed by
Teare (2010), the changes made to the OSPFv3 include the following:
In OSPFv3, the
multicast addresses reserved for all SPF or link state routers and all
designated routers are now FF02::5 and FF02::6 respectively; they are no
longer 22.214.171.124 and 126.96.36.199 as used in OSPFv2 for IPv4.
The packet header of
OSPFv3 is not designed to include IPv6 addresses. Rather, IPv6 address is
carried inside the payload of the link state update packet.
In OSPFv2, network
LSAs carry IPv4 addresses but in OSPFv3, network LSAs do not include IPv6
To configure OSPFv3
on routers, the router ID must be enabled before routing can start.
identification of the designated router and backup designated router is
done with the router’s ID; not with its IP address as in the case of