Operation Manual

from the information made available by the neighboring routers, relying on a pro-
tocol called the neighbor discovery (ND) protocol. This method does not require
any intervention on the administrator's part and there is no need to maintain a central
server for address allocation—an additional advantage over IPv4, where automatic
address allocation requires a DHCP server or the usage of ARP and 169.254.0.0/16
addresses.
Nevertheless if a router is connected to a switch, the router should send periodic
advertisements with ags telling the hosts of a network how they should interact
with each other. For more information, see RFC 2462 and the radvd.conf(5)
manpage, and RFC 3315.
Mobility
IPv6 makes it possible to assign several addresses to one network interface at the
same time. This allows users to access several networks easily, something that
could be compared with the international roaming services offered by mobile phone
companies: when you take your mobile phone abroad, the phone automatically
logs in to a foreign service as soon as it enters the corresponding area, so you can
be reached under the same number everywhere and are able to place an outgoing
call just like in your home area.
Secure Communication
With IPv4, network security is an add-on function. IPv6 includes IPsec as one of
its core features, allowing systems to communicate over a secure tunnel to avoid
eavesdropping by outsiders on the Internet.
Backward Compatibility
Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6
at one time. Therefore, it is crucial that both protocols are able to coexist not only
on the Internet, but also on one system. This is ensured by compatible addresses
(IPv4 addresses can easily be translated into IPv6 addresses) and through the use
of a number of tunnels. See Section 23.2.3, “Coexistence of IPv4 and IPv6”
(page 370). Also, systems can rely on a dual stack IP technique to support both
protocols at the same time, meaning that they have two network stacks that are
completely separate, such that there is no interference between the two protocol
versions.
Custom Tailored Services through Multicasting
With IPv4, some services, such as SMB, need to broadcast their packets to all hosts
in the local network. IPv6 allows a much more ne-grained approach by enabling
Basic Networking 365