Information Technology Reference
In-Depth Information
string of 0 values—in this case, a string of three consecutive 0 values. The rest of the address
(64 bits) has been randomly assigned by Windows.
4. Type
ping ::1
and press
Enter
. Windows replies because you just pinged your own computer.
Type
ping -a ::1
and press
Enter
. The -a option tells Windows to display the hostname for
the ::1 address, which is the name of your Vista computer.
5. Type
ping -6 serverXX
and press
Enter
. The -6 option tells Ping to use IPv6 addresses. You
should receive a reply from your server. Now ping your server by using the IPv6 address the
previous ping replied with. You can include the %8 at the end of the address or omit it.
6. Type
getmac
and press
Enter
to display your computer's MAC address. Make a note of this
address.
7. Type
netsh interface ipv6 set global randomizeidentifiers=disabled
and press
Enter
.
8. Type
ipconfig
and press
Enter
. Notice that the last 64 bits of the IPv6 address now look like
your MAC address, with the addition of FF-FE after the first 24 bits and 02 instead of the
first 00 of your MAC address.
9. Close the command prompt window, and log off.
Subnetting with IPv6
Although subnetting as done in IPv4 will be a thing of the past,
it doesn't mean subnetting won't be used at all in IPv6 networks. Typically, ISPs allocated IPv4
addresses to businesses in groups specified by a network address and IP prefix. ISPs try to give
a business only the number of addresses it requires. However, with IPv6 having such a large
address space, most address allocations will have a /48 prefix, even for small home networks.
This means the network ID is 48 bits, and the network administrator has 80 bits for assigning
subnets and host IDs. Because the host ID is 64 bits, 16 bits are left for creating subnets. This
number of bits allows for 65,536 subnets, more than enough for all but the largest organiza-
tions. Large conglomerates can get multiple /48 prefix addresses or /47 prefix addresses, which
provide more than 130,000 subnets. A typical IPv6 address, then, as assigned by an ISP looks
like Figure 8-15.
Global routing prefix (48 bits)
Subnet ID (16 bits)
Interface ID (64 bits)
Figure 8-15
Structure of a typical IPv6 address
With 16 bits available to subnet, there are many strategies you can use. A small network that
doesn't have multiple subnets can simply leave the subnet ID as all 0s, for example, and an
address in this situation might look like this:
2001:DB8:A00:0000:020C:29FF:FE7C:F9C4/64
This address begins with 2001:DB8, which is not random. The IPv6 developers realized
that people will be writing about how to work with IPv6, so instead of authors using random
values for examples, they reserved 2001:DB8 for use in documentation. The A00 in the
address is the last 16 bits of the network prefix and was randomly chosen for this example.
The 0s following the A00 are the subnet ID, and the last 64 bits are the computer's interface
ID. The /64 just indicates that the network portion of the address is the first 64 bits (network
prefix plus subnet ID).
A network that does need to subnet could just take the 16 bits for the subnet ID and start
counting. For example, a company could make the first three subnets as follows; the bold part
of the address is the subnet ID, and the 64-bit interface ID has been omitted.
• 2001:DB8:A00
:0000
• 2001:DB8:A00
:0001
• 2001:DB8:A00
:0002
Search WWH ::
Custom Search