DHCP Scopes
Adding a Scope
To add a new scope:
- Select the DHCP settings configuration.
- Right-click the interface on which you wish to add a scope.
- Choose New Scope.
- Follow Changing Scope properties (below).
Changing Scope Properties
You can change the properties of an existing scope. You can extend the address range of the scope, but you should not reduce it. You can, however, exclude any unwanted addresses from the range.
To Define the Properties of a DHCP Scope:
- Select the DHCP settings tab.
- Double click the scope you want to change.
- The scope properties configuration will be displayed.
- Configure the Scope properties as required.
General Properties:
The Description is a unique name for this scope. This will be displayed in the DHCP options window. The Scope enabled option enables/disables allocation from this scope.
- Allocate IP addresses in the range Properties:
- This is the range of IP addresses to allocate to clients. 192.168.0.* is the default, as is the Network Mask of 255.255.255.0. If you wish to use different options for the range or mask, see the advanced sections.
- Lease Duration Properties:
- The default lease time is 3 days. This is a suitable time for most LANs. If you have a LAN with more computers than the size of your scope, you may wish to have the lease period short. This will enable the available IP's to be shared around.
- Excluded Addresses Properties:
- These are IP's within the scope range that you do not wish to allocate to client computers. In the example above, the IP address 192.168.0.100 and all the IP addresses from 220* 240 will not be allocated.
To add an exclusion:
- In the Scope properties configuration, type the IP number you wish to exclude into the From field.
- To exclude a range, type in an end address into the To field.
- Click Add.
Removing a Scope
When a subnet is no longer in use, or if you want to remove an existing scope, you can remove it from the DHCP service. It is recommended that you deactivate a scope until you know that no leases are current before deleting it.
To Remove a Scope:
The scope should be deactivated until you are sure the scope is not in use.
- On the Scope list in the DHCP window, select the scope you want to remove.
- On the Scope menu, click Delete.
Assigning DHCP Configuration Options
Besides the IP addressing information, other DHCP options to be passed to DHCP clients must be configured for each scope, or globally under the Global Options. options can be defined globally for all scopes, specifically for a selected scope, or for individual DHCP clients:
- Active global option types always apply, unless overridden by scope or DHCP client settings.
- Active option types for a scope apply to all computers in that scope, unless overridden for an individual DHCP client.
Only configure options if you know what effect if will have on DHCP. Some Options are inter-related (see the DHCP Configurable Options List ).
To Assign DHCP Configuration Options:
- In the DHCP Service/Settings tab/Settings, double click the scope you want to configure, or click global to configure all, or click a specific reservation
- Click Options.
- For options that you wish to configure, use the Add button to add options from the Available to the In use lists.
- Double click an in use option name to edit it.
- Enter the relevant information.
- Click OK.
Example:
To specify the DNS name servers to be used by DHCP clients, double click DNS Server and then type an IP address for a DNS server in the edit box and click add. The list should be in the order of preference, so that the first server in the list is the first server to be consulted.
To Remove a Configured Option:
- Select the option and click removal.
- Click OK.
Note on WINS Server:
If you specify a WINS Server, you must also configure a NBT Node type.
