IPV6 Tutorial–part 8:special Addresses

https://4sysops.com/archives/ipv6-tutorial-part-8-special-addresses/

The special IPV6 addresses discussed in this part of the IPV6 tutorial is the unspecified address, the loopback address, Ipv4-mapped addresses, 6to4 addresses, multicast addresses, and the Solicited-node address.

Last time, I talked about zone IDs and unique local IPv6 unicast addresses.

Today, I'll introduce some special addresses.

In practice, usually only the networking guys really has to deal with these addresses.

But as a Windows admin, you should has at least heard of the terms.

Unspecified Address

The IPV6 unspecified address is specified as "0:0:0:0:0:0:0:0" (or "::" If you had a sense for mathematical beauty).

I think, this naming convention is somewhat funny. It reminds me of the "unspeakable word."

But there was also some sense in this because applications use the unspecified address as a variable for, well, an UNSPECIF IED address.

I guess, you won ' t see this address often, just like you didn ' t has many encounters with the unspecified IPv4 address 0.0 .0.0.

Note that you can ' t assign the address to a interface, which also makes sense because then you would specify it, which I s strictly forbidden.

Loopback Address

Like the loopback address, ipv4-mapped addresses is only used for internal representation on a host.

They allow developers to use one API for both IPV4 and IPV6 calls.

The syntax of ipv4-mapped addresses looks like this:: Ffff:w.x.y.z, where "w.x.y.z" is the IPV4 address, which is Represente D in the IPV6 address.

6to4 Addresses

6to4 is a tunneling technique that allows, IPV6 cable systems to communicate over an IPV4 network (usually the Internet ).

For this, at least one of the IPV6 systems needs an IPV4 address and a special IPV6 address, the so-called 6to4 address.

A computer that have a 6to4 address is called "6to4 host." This transition technology would mostly likely be used by computers in IPV4 networks to reach Ipv6-only hosts.

Essentially, the 6to4 address makes the 6to4 host appear on the "IPv6 landscape" even if it's not directly reachable thro Ugh IPV6 by encapsulating IPV6 packets in IPV4 packets.

The IPV4 packets is converted to IPV6 packets and vice versa by a 6to4 gateway.

6to4 addresses has the prefix 2002::/16. The next + bits is the IPV4 address of the 6to4 host converted into Hex.

Since A 6to4 address can only being created by using a unique public IPv4 address, the corresponding IPV6 address is also uni Que. The last bits is for the local network and the host.

IPV6 Multicast Addresses

Like in IPv4, IPV6 multicast addresses is used to send the same data to multiple hosts simultaneously.

Since multicast-capable software, such as OS imaging tools, typically do all the IP configuration, Windows admins usually is not a bothered with the networking details.

But if you ever stumble across a IPv6 address that begins with FF, you know what is dealing with.

Solicited-node Address

A special type of multicast address is the Solicited-node addresses, which has the prefix ff02::1:ff00:0/104.

Solicited-node addresses is used for neighbor Discovery, which I already discussed on my article about the new IPV6 Featu Res.

If a host needs to know the MAC address this belongs to a certain IP address, it won ' t use a ARP broadcast like in IPv4.

Instead, it would use multicast to contact only those hosts the listen to the solicited-node where the Last bits is identical to the ones in the IP address of that have to is resolved.

IPV6 Tutorial–part 8:special Addresses