Multicast Support for Remote Access Clients

A common use for the Windows 2000 IGMP routing protocol is to provide multicast services to dial-up or virtual private network (VPN) remote access clients. As in the previously discussed configurations, the remote access or VPN server is acting as a peripheral router to a multicast-enable IP internetwork.

There are two possible configurations, depending on the connectivity provided to the remote access clients:

• MBone access for dial-up clients by an ISP.
• Access to a private multicast-enabled intranet for dial-up or VPN clients.

MBone Access for ISP Dial-Up Clients

If you are using the Windows 2000 Routing and Remote Access service to provide Internet access to dial-up clients as an ISP:

1. Add the Internal interface, and the interface connecting to the rest of the Internet, to the IGMP routing protocol. The Internal interface represents all remote access clients.
2. Configure the Internal interface for IGMP router mode.
3. Configure the Internet interface for IGMP proxy mode.

Connected remote access clients joining multicast groups send IGMP Host Membership Reports, which are copied on the Internet interface. Multicast traffic from the Internet is sent to the Internet interface. When received, the multicast traffic is forwarded to the connected host. Multicast traffic sent by a connected host is forwarded to other connected host group members and copied to the Internet interface. The downstream multicast router in the Internet either ignores the multicast traffic or forwards it to downstream group members.

The MBone access configuration for ISP dial-up clients is shown in Figure 4.9.

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Figure 4.9 MBone Access for ISP Dial-Up Clients

Private Intranet Access for Dial-Up or VPN Clients

If you are using the Windows 2000 Routing and Remote Access service to provide intranet access for dial-up or VPN remote access clients, perform the following steps:

1. Add the Internal interface and the interface connecting to the private intranet to the IGMP routing protocol. The Internal interface represents all remote access clients. The private intranet interface must be attached to a subnet containing a multicast core router.
2. Configure the Internal interface for IGMP router mode.
3. Configure the private intranet interface for IGMP proxy mode.

Connected remote access clients joining multicast groups, send IGMP Host Membership Reports, which are copied on the intranet interface. Multicast traffic from the intranet is sent to the IGMP proxy mode interface subnet. When received, the multicast traffic is forwarded to connected group members. Multicast traffic sent by a connected host is forwarded to other connected host group members and copied to the IGMP proxy mode interface subnet. The multicast core router either ignores the multicast traffic or forwards it to downstream group members.

The private intranet access for dial-up or VPN clients configuration is shown in Figure 4.10.

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Figure 4.10 Private Intranet Access for Dial-Up or VPN Clients

For more information about multicast support for the remote access server, see "Remote Access Server" in this book.

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