Unexplained BOOTP Broadcasts Using NT and RAS

 Last reviewed: August 23, 1996
Article ID: Q150281
The information in this article applies to:
  • Microsoft Windows NT operating system version 3.1
  • Microsoft Windows NT Advanced Server version 3.1
  • Microsoft Windows NT Workstation versions 3.5 and 3.51
  • Microsoft Windows NT Server versions 3.5 and 3.51

SYMPTOMS

BOOTP broadcasts are being inserted onto the network. The source MAC address for these packets begins with 5, but none of the network cards on the network have MAC addresses that match the source MAC address of the BOOTP packets.

CAUSE

The likely cause of this is the Remote Access Service (RAS). When you configure a RAS server for dial-in with the TCP/IP protocol, Windows NT will, by default, attempt to obtain IP addresses for the RAS service using Dynamic Host Configuration Protocol (DHCP). NT will send DHCP requests every two minutes until it successfully obtains addresses for the RAS service. When there is no DHCP server available on the network, NT will continue to send DHCP requests indefinitely.

Both DHCP and BOOTP use User Datagram Protocol (UDP) port 67. Because of this, DHCP requests are frequently interpreted to be BOOTP requests.

RESOLUTION

You can resolve this problem by statically configuring IP addresses for your RAS servers. To do this you must first stop the Remote Access Service, which is done by performing the following steps:

  1. From Control Panel, choose Services.
2. From the list of services, select "Remote Access Server." 3. Click on the Stop button. 4. When NT asks "Are you sure you want to stop the Remote Access Server 
  Service?" select "Yes."
5. After the service stops, click the "Close" button.

When RAS is closed, you must then specify an IP address range for the RAS server, which is done by performing the following procedure:

  1. From Control Panel, choose Network.
2. In the Installed Network Software dialog box, select "Remote Access 
  Service."
3. Click on the "Configure" button. 4. Select the first RAS port that is configured for dial-in. 5. Click on "Network." 6. Under the Server Settings, click on "Configure" next to TCP/IP. 7. Choose the "Use static address pool" button and specify an IP 
   address range on the same subnet as the RAS server. (The address
   range must have at least as many unused IP addresses as the number
   of dial-in ports, plus one. For example, a machine which has two dial-in
   ports configured must have at least three IP addresses defined in the
   static address pool.)
8. Select "OK," "OK," "Continue," and "OK." 9. Restart the computer after it completes its bindings checks.

To complete the entire process, restart RAS as needed.

Repeat the above procedure on every RAS server that is configured for dial- in using TCP/IP.

KBCategory: kbnetwork
KBSubcategory: ntconfig ntnetserv ntras ntprotocol NTSrvWkst
Additional reference words: sniff trace netmon



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Last reviewed: August 23, 1996
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