IPv6 Tutorial–part 7:zone ID and unique local IPV6 unicast addresses

The zone ID is used to distinguish ambiguous link-local and site-local addresses.

Unique Local IPV6 unicast addresses is another to address the problem of ambiguous IPv6 addresses.

The Last post of this IPv6 tutorial, I introduced link-local and site-local IPv6 addresses.

The problem with Local-use unicast addresses was that they was not a unique because they can be reused.

Everything is fine as long as duplicate addresses be in networks of different organizations (sites).

However, within in a organization, Local-use addresses can also be assigned multiple times.

IPV6 Zone ID

NIC is short for network Interface card network card

The purpose of zone IDs is to distinguish these addresses.

For instance, if host A has both NICs that is connected to the different links (subnets),

The same Local-link address could has been used for NIC 1 on host A And on host B

That[the same Local-link address] is on the link of host A ' s NIC 2.

To distinguish this ambiguous link-local address, host A uses the interface index of NIC 1 as the zone ID for the Local IP address.

For site-local addresses, the operating system uses the site ID (also called the Scope ID).

If A host is the only connected to one site, the This ID is always 1.

You can display the interface indexes in a host with the command "netsh interface ipv6 show address Level=verbose ”.

If you launch the ipconfig command, you can see the Local-link and site-local addresses with their zone IDs.

The syntax for identifying, the zone is address%zone_id.

A example of a link-local IP address with zone ID 11:fe80::bd0f:a8bc:6480:238b%11.

Note that the zone IDwas only known at the local host, that assigned it.

I think in practice you'll seldom be bothered with zone IDs as you don't have to configure them manually.

Unique Local IPV6 unicast address

Even with the as zone IDs, you should probably avoid have ambiguous IP addresses in your network.

Instead of site-local addresses, you can work with unique local IPV6 unicast addresses.

These local-use addresses is also not routed across the Internet; However, like global IPv6 addresses, they is unique. Well, more or less, as you'll soon see.

The prefix of unique local IPv6 unicast addresses is FC00::/7.

The eighth bit is the local flag and are set to 1 for Local addresses.

A Local flag with 0 have not yet been defined.

Perhaps this could is a-to-make local IPV6 addresses global?

Anyway, until IPv6, creators has made up their mind, the prefix of unique local IPv6 unicast addresses is FD00::/8.

Don ' t worry if you don't really understand this; All you really has to know about unique local IPV6 unicast addresses are this:

The next-bits is for the global ID and is randomly set.

The following is the subnet ID, which you can use a for hierarchical addresses within your organization. As usual, the last bits is the interface ID.

The trick with the random global ID is so it makes it somewhat unlikely for duplicate local addresses to occur on a site Or even in the networks of the merging organizations.

Actually, the probability that both organizations use the same global ID for their unique local IPv6 addresses is 1/240=9.1 10-13.

Winning The Lotto jackpot is a few magnitudes more likely.

However, what's the IPv6 creators didn ' t take to account was that Murphy's law rules Murphy's laws in all networks.

Hence, "relatively unique local IPv6 unicast addresses" would probably has been a better name.

In the next post on this IPv6 tutorial, I'll discuss the special IPv6 addresses:unspecified address, ipv4-mapped addres s, 6to4 addresses, IPV6 multicast address, and Solicited-node address.

IPv6 Tutorial–part 7:zone ID and unique local IPV6 unicast addresses