JSI Tip 7419. When you enable Internet Group Management Protocol (IGMP) support (multicast) within the Routing and Remote Access Service (RRAS), Event ID 20157 is generated?

When you perform the subject action, the event log contains:

Event ID: 20157
Source: IPRouterManager
Description: The interface {Interface Global Unique Identifier (GUID)} could not be enabled for multicast. IGMP will not be activated over this interface.

If your computer uses a network adapter that does not have the ability to see all the network packets (promiscuous mode), not just the packets destined for it, you will experience this problem, as the adapter cannot listen to multicast traffic.

NOTE: Some adapter manufacturers have 2 device drivers, one that supports promiscuous mode, and one that does not.

NOTE: To enable IGMP support in RRAS:

1. Use the Administrative Tools menu to start the Routing and Remote Access.

2. Expand the RRAS server name.

3. Expand IP Routing.

4. Right-click the network adapter and press Properties.

5. Select the General tab.

6. Check the options you desire.