HOW TO: Set Up Multiple-Device (Multilink) Dialing in Windows XP

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This article describes how to configure multiple-device dialing in Windows XP.

With Windows XP, you can use multiple modems to connect to your Internet service provider (ISP) to increase the total speed of your transfers. Multiple-device dialing (also known as Multilink PPP, modem aggregation, or Multilink) causes multiple physical links to be combined into one logical link. Typically, two or more ISDN lines or modem links are bundled together for greater bandwidth. You might use this feature if you do not have access to DSL or cable services.

Multilink is enabled automatically in Windows XP Home Edition and Windows XP Professional.


To use multiple device dialing:
  • Your ISP must support synchronization of multiple modems.
  • You need to install multiple modems.
  • You need a separate phone line for each modem.
Note that a single ISDN adapter can act as multiple devices because ISDN includes two 64-Kbps B channels, which can be used independently or together.

Configuring Multiple-Device Dialing

The Network Connections feature performs Point-to-Point (PPP) Multilink dialing over multiple ISDN, X.25, or modem lines. This feature combines multiple physical links into a logical bundle; the resulting aggregate link increases your connection bandwidth. To dial multiple devices, both your connection and your remote access server must have Multilink enabled.

Network Connections can dynamically control the use of lines that are using Multilink. By allocating lines only as they are required, excess bandwidth is eliminated. You can configure the conditions under which extra lines are dialed, and underused lines are hung up, by changing Network Connections settings.

Note that if you use Multilink to dial a server that requires callback, only one of your Multilink devices is called back. This occurs because you can store only one number in a user account. Therefore, only one device connects and all other devices do not connect; your connection loses Multilink functionality. You can avoid this problem:
  • If the phonebook entry for the Multilink connection uses a standard modem configuration, and the remote access server that your connection is calling uses more than one line for the same number.
  • If the phonebook entry for the Multilink connection is ISDN with two channels that have the same phone number.
To configure a connection:
  1. Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
  2. Click the connection that you want to configure (for example, a dial-up connection), and then, under Network Tasks, click Change settings of this connection.
  3. Click the General tab, and then click each device that you want to use for this connection.
  4. Use one or more of the following steps:
    • To configure dialing devices, phone numbers, the host address, country or region codes, or dialing rules, click the General tab.
    • To configure dialing and redialing options, or X.25 parameters, click the Options tab.
    • To configure identity authentication, data encryption, or terminal window and scripting options, click the Security tab.
    • To configure the remote access server and protocols that are used for this connection, click the Networking tab. Also, click Settings and select the Negotiate multi-link for single link connections check box.
    • To enable or disable Internet Connection Sharing, Internet Connection Firewall, and on-demand dialing, click the Advanced tab.
  • Depending on the type of connection that you are configuring, different options and tabs appear in the connection's properties.
  • For more information about a specific item on a tab, right-click the item, and then click What's This?


Article ID: 307849 - Last Review: July 23, 2004 - Revision: 3.1
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
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