Thread: Creating Multicast Scopes in Windows Server 2008

Creating Multicast Scopes in Windows Server 2008

A multicast scope is used to broadcast IP traffic to a group of nodes using a single address, and is traditionally used in audio and video conferencing. Using multicast addresses simplifies administration and decreases network traffic because the data packets are sent once to the multicast address, rather than individually to each recipient’s unicast address.

A Windows Server 2008 DHCP server can allocate multicast addresses to a group of computers much as it allocates unicast addresses to individual computers. The protocol for multicast address allocation is Multicast Address Dynamic Client Allocation Protocol (MADCAP). Windows Server 2008 can function independently as both a DHCP server and a MADCAP server.

For instance, one server may use the DHCP service to allocate unicast addresses through the DHCP protocol, and another server may allocate multicast addresses through the MADCAP protocol. In addition, a client can use either or both. A DHCP client doesn’t have to use MADCAP, and vice versa, but a client can use both if the situation requires it.

You can create multiple multicast scopes on a Windows Server 2008 DHCP server as long as the scope address ranges don’t overlap. Multicast scopes exist directly under the server branch and cannot be assigned to superscopes, which are intended only to manage unicast address scopes.

To create a multicast scope, open the DHCP console, right-click the server in which you want to create the multicast scope, and choose New Multicast Scope. Windows Server 2008 starts a wizard that prompts you for the following information:

1) Name: This is the friendly name as it appears for the scope in the DHCP console.
2) Description: Specify an optional description to recognize the purpose of the multicast scope.
3) Address Range: You can specify an address range between 224.0.0.0 and 239.255.255.255, inclusive, which provides you a large range of addresses to use.
4) Time to Live (TTL): Specify the number of routers the traffic must pass through on your local network.
5) Exclusion Range: You can define a range of multicast addresses to exclude from the scope, just as you can exclude unicast addresses from a DHCP scope.
6) Lease Duration: Specify the duration for the lease. The default is 30 days.

You can choose to activate the scope through the wizard or activate the scope later. Right-click a multicast scope and choose Activate to activate the scope.