Setting up a multicast forwarder in Windows Server 2008



The first step in configuring a multicast forwarder is to add the IGMP (Internet Group Management Protocol) protocol to the router. In the RRAS console, open the IP Routing branch of the designated server, right-click General, and choose New Routing Protocol. Select IGMP from the list and click OK to add it to the IP Routing branch.

Next, add at least one interface for IGMP. Right-click IGMP in the left pane and choose New Interface. Alternatively, select IGMP in the left pane and right-click anywhere in the right pane and choose New Interface. Select the interface on which you want to run IGMP and click OK. RRAS displays the IGMP Properties sheet. The General tab permits you to choose between router mode and proxy mode for the interface. Select the protocol version using the IGMP Protocol Version drop-down list if you select router mode.

The Router tab includes several options that control how IGMP functions on the interface:

1) Robustness Variable: This variable shows the relative robustness of the subnet to which the interface is attached.
2) Query Interval: Specify the interval at which IGMP queries are broadcast on the interface.
3) Query Response Interval: Specify the maximum amount of time the router should wait for a response for General Query messages.
4) Last Member Query Interval: Specify the time, in milliseconds, the router waits for a response to a Group-Specific Query message, and the time between successive Group-Specific Query messages.
5) Startup Query Interval: Specify the time, in seconds, between successive General Query messages sent by the router during startup. The default value is one-quarter of the query interval.
6) Startup Query Count: Specify the number of General Query messages to send at startup.
7) Last Member Query Count: Specify the number of Group-Specific Query messages sent with no response before the router assumes there are no more members of the host group on the interface being queried.
8) Automatically Recalculate Defaults: Select this option to have RRAS automatically re-calculate values for the Startup query interval, Startup query count, and Last member query count at startup. The default for the Startup query interval is one-quarter the query interval. The default for Startup query count and Last member query count is the same as the Robustness variable.
9) Group Membership Interval: This read-only property displays the calculated group membership interval, which is the period of time that must pass before the router decides that there are no more members of a multicast group on a given subnet. The value is calculated as (Robustness variable) × (Query interval) + (Query response interval).
10) Other Querier Present Interval: This read-only property displays the calculated querier present interval, which is the amount of time that must pass before the router decides that there are no other multicast routers that should be the querier. The value is calculated as (Robustness variable) × (Query interval) + (Query response interval) ÷ 2.