Now that you’ve seen how to create a new scope in IPv4, I’ll go through the steps to create a new scope in IPv6.
To create a scope, right- click the IPv6 option in the DHCP snap- in under the server name and select the Action ➢ New Scope command. This starts the New Scope Wizard. Just as with creating a scope in IPv4, the welcome page of the wizard tells you that you’ve launched the New Scope Wizard. You will look at each page of the wizard in the following sections.
Setting the Screen Name
The Scope Name page (see Figure 6.14) allows you to enter a name and description for your scope. These will be displayed by the DHCP snap- in.
FIGURE 6.14 IPv6 Scope Name page of the New Scope Wizard
Scope Prefix
The Scope Prefix page (see Figure 6.15) gets you started creating the IPv6 scope. IPv6 has three types of addresses, which can be categorized by type and scope:
FIGURE 6.15 Scope Prefix page of the New Scope Wizard
Unicast Addresses One- to- one. A packet from one host is delivered to another host. The following are some examples of IPv6 unicast:
■ The unicast prefix for site- local addresses is FEC0::/48.
■ The unicast prefix for link- local addresses is FE80::/64.
The 6to4 address allows communication between two hosts running both IPv4 and IPv6. The way to calculate the 6to4 address is by combining the global prefix 2002::/16 with the 32 bits of a public IPv4 address of the host. This gives you a 48- bit prefix. 6to4 is described in RFC 3056.
Multicast Addresses One- to- many. A packet from one host is delivered to multiple hosts (but not everyone). The prefix for multicast addresses is FF00::/8.
Anycast Addresses A packet from one host is delivered to the nearest of multiple hosts (in terms of routing distance).
Adding Exclusions
As with the IPv4 New Scope Wizard, the Add Exclusions page allows you to create exclusion ranges. Exclusions are TCP/IP numbers that are in the pool but do not get issued to clients. To exclude one address, put it in the Start IPv6 Address field. To exclude a range, also fill in the End IPv6 Address field.
Setting a Lease Duration
The Scope Lease page allows you to set how long a device gets to use an assigned IP address before it has to renew its lease. You can set two different lease durations. The section labeled Non Temporary Address (IANA) is the lease time for your more permanent hosts (such as printers and server towers). The one labeled Temporary Address (IATA) is for hosts that might disconnect at any time, such as laptops.
Activating the Scope
The Completing The New Scope Wizard page gives you the option to activate the scope immediately after creating it. By default, the wizard will assume you want the scope activated. If you want to wait to activate the scope, choose No in the Activate Scope Now box.
Changing Scope Properties (IPv4 and IPv6)
Each scope has a set of properties associated with it. Except for the set of options assigned by the scope, you can find these properties on the General tab of the scope’s Properties dialog box (see Figure 6.16). Some of these properties, such as the scope name and description, are self- explanatory. Others require a little more explanation:
FIGURE 6.16 General tab of the scope’s Properties dialog box for an IPv4 scope
■ The Start IP Address and End IP Address fields allow you to set the range of the scope.
■ For IPv4 scopes, the settings in the section Lease Duration For DHCP Clients control how long leases in this scope are valid.
The IPv6 Scope dialog box includes a Lease tab where you set the lease properties.
When you make changes to these properties, they have no effect on existing leases. For example, say you create a scope from 172.30.1.1 to 172.30.1.199. You use that scope for a while and then edit its properties to reduce the range from 172.30.1.1 to 172.30.1.150. If a client has been assigned the address 172.30.1.180, which was part of the scope before you changed it, the client will retain that address until the lease expires but will not be able to renew it.
Changing Server Properties
Just as each scope has its own set of properties, so too does the server itself. You access the server properties by right- clicking the IPv4 or IPv6 object within the DHCP Management Console and selecting Properties.
IPv4 Server Properties
Figure 6.17 shows the IPv4 Properties dialog box.
FIGURE 6.17 The General tab of the IPv4 Properties dialog box for the server
The IPv4 Properties dialog box has five tabs: General, DNS, Filters, Failover, and Advanced. The Advanced tab, shown in Figure 6.18, contains the following configuration parameters:
■ Conflict Detection Attempts specifies how many ICMP echo requests (pings) the server sends for an address it is about to offer. The default is 0. Conflict detection is a way to verify that the DHCP server is not issuing IP addresses that are already being used on the network.
■ Audit Log File Path is where you enter the location for log files.
■ Change Server Connection Bindings allows you to choose which of the network adapters will be used by the DHCP server for both IPv4 and IPv6 addresses.
■ DNS Dynamic Update Registration Credentials allows you to put in user credentials so that DHCP can update DNS if DNS is using Secure Only dynamic updates.
FIGURE 6.18 Advanced tab of the IPv4 Properties dialog box for the server
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