This Technote outlines the problems and situations related to Dial on Demand (DOD) with a Netopia ISDN and Dual Analog routers.
Dial on Demand presents a problem when spurious traffic from the Local Area Network (LAN) causes the Netopia router to dial out and connect, or stay connected when users are not actively using the Wide Area Network (WAN) connection. Traffic from the WAN side of the Netopia can also cause a connection to stay connected. However this type of problem is covered only briefly in this Technote.
The sections of this Technote describe some circumstances that may cause a connection to stay up as well as solutions, if they are available. While this Technote does not outline all the possible problems that you may have when using DOD, it is intended to assist in locating the source of a problem and provide fixes to well-known problems. If this Technote does not resolve your problem, it may be necessary to have a consultant investigate the issue further to locate the source of the problematic traffic.
Below is a list of hardware and firmware loads that this Technical Note is based upon:
| Hardware | Firmware/Version | Installed Options |
| Any Netopia ISDN or Analog Router | Any | Dial on Demand |
Many Netopia customers are using a feature called Dial on Demand (DOD). DOD is a feature that allows users to have access to the Internet without having to worry about manually establishing a connection to the Internet. This feature relies on IP or IPX traffic from the LAN to initiate the dial on demand connection which can sometimes cause excessive connections if there is spurious traffic from the LAN.
The technical details of DOD are outlined in NIR_020: Dial on Demand Routing. We recommend referencing that document if you have additional questions about how DOD functions.
Using DOD is not generally problematic, however there are some circumstances which will generate problems. These problems are outlined the following section titled Problem Scenarios. If applicable, a solution is presented. The solutions that are presented assume that you know what the source of the traffic is and that you know what type of traffic is causing this problem to occur. If you have not determined what type of traffic is causing the connection to be established or you do not know the source of the traffic, please reference the section below titled Locating the source of traffic from your LAN.
Prior to troubleshooting a LAN problem, you should make sure that the traffic is actually being generated from your LAN and not the WAN. You can determine this by simply unplugging the Ethernet cable from the Netopia and seeing if the problem disappears. If so, then the source of the traffic is your LAN. If not, then it is likely that the source is either from the Internet or the router itself.
Below is a list of scenarios that may cause problems with DOD configurations.
Router does not time-out:
- Router may be configured with a Scheduled Connection that causes it to fail to time-out.
Solution: Remove the Scheduled Connection.
- Router may be configured to establish and maintain an AURP tunnel, which generates traffic on a regular basis.
Solution: Make sure the Tickle Packet Interval in the AURP setup is set for the longest interval (99:59:59 hours).
- Traffic is being generated from the ISP or Internet that may be maintaining the connection.
Solution: You may be able to find out what type of traffic is causing the connection to stay up and filter it out. You may also want to reference NQG_016, which explains one common cause of this problem.
Router does not time-out or connects when there appears to be no network traffic:
- NetBIOS broadcasts from one or more Windows 95/98/NT workstation. This is the protocol used to communicate the machine names and transfer files that you see in Network Neighborhood.
Solution: You may reference NIR_025 for help on blocking this type of traffic.
- TCP/IP applications may cause problems if they are configured to communicate with the internet at specified intervals. Other applications that communicate with the Internet may also cause DOD problems, even if they are not actively being used. A list of known problematic applications are listed below in the section below, titled Applications that may cause problems with Dial On Demand on your Network.
Solution: Reconfigure the application to stop unnecessary Internet communication or remove the application from the computer.
- A mail server on your network that pulls mail from the ISP will cause the router to dial out and connect when the server attempts to get mail. There may also be other functions that servers and clients perform that will initiate communication over the WAN.
Solution: Mail servers must connect to get mail and therefore will cause the router to dial, so the Mail Server should be configured to check mail at as large a time interval as practical.
Applications that may cause problems with Dial On Demand on your network:
The following is a list of applications known to generate traffic that causes the router to dial out and connect, if not properly configured.
- Netscape, Eudora, and other mail or web application - If any of these applications are configured to check mail on a regular basis or if they sit at a web site that auto-updates or has animated gifs, this can cause the Netopia to dial out and connect or stay connected. Netscape has a Magic Cookie file that has been known to cause problems by polling certain Internet sites when Netscape is not in use. This Magic Cookie file can be removed or you can remove any specific cookie that is causing this problem to occur.
- Other Netscape extensions (Mac) - Netscape Communicator Audio Tune-up, QTCH245 Library, and SNMP QT Agent have all been known to cause problems with Dial On Demand.
- Norton Utilities - Some versions of Norton Utilities will send ping (ICMP) packets to a Norton site at regular intervals and cause your connection to stay up or dial up unexpectedly.
- Pointcast - This is an information gathering application. Therefore is constantly polling sites on the Internet for information.
- Windows 98 Active Desktop - Since Active Desktop is an interactive, network related tool, it has a number of options that will cause it to initiate traffic to the Internet.
- Real Audio Suite - As this is a streaming application used for listening to radio stations and such, if left running it can and will make the Netopia router stay connected for an indefinite period of time.
- NetMedic - This application probes the LAN and WAN using various protocols to determine the state of the Network and your ISP's network. This probing process often causes a connection to be maintained for long periods of time.
- Quake, Doom and other Network Games - As these games search for other players on the Internet, they can often cause an Internet connection to be maintained for long periods of time, if left running.
This is by no means a complete list of all applications which may cause this problem. Any application which communicates via TCP/IP mat cause these problems to occur. If none of the circumstances listed above apply to you, then the following section should provide some assistance in locating the source of traffic.
This section describes the process involved in locating the source and type of traffic that is causing your router to connect or stay connected. This is intended as a guide to troubleshooting these problems, but is by no means a step-by-step walk-through of the process. If, after trying the steps that have been suggested here, you are still unable to locate the source of the traffic, then it may be necessary to have a consultant troubleshoot the problem more thoroughly.
First, determine which machine or machines are generating the traffic. This can be done in a number of ways. The Netopia creates an event in the WAN event history when traffic from a local machine causes the router to dial out and connect. This event will display the source and destination IP address as well as the date and time. If the Netopia is connecting on a regular basis, refer to this log to see if just a single machine is causing these connections or if it is caused by multiple different machines.
If the Netopia is simply not disconnecting, you may need to turn the router off and back on and watch to see which machine causes it to dial out. If it is a single machine, then you can locate the problem rather easily by simply shutting down applications until the problem stops, if that does not fix the problem then you will likely need to run a packet sniffer to locate the type of traffic that the machine is generating.
If multiple machines are generating traffic, you will need to first determine if they are all generating the same type of traffic or if the traffic is from different sources. You can normally do this by simply examining the destination IP address (this can be done by selecting the event with the arrow keys and pressing enter) in the WAN event history to determine if they are all trying to get to the same place. If they are attempting to get to different locations, chances are that the traffic is going to be of different types. If this is the case, each machine should be dealt with individually, attempting to locate the source of traffic on each machine and correct the application that is generating it.
There are a number of different types of traffic that can cause a Netopia router to dial out and connect. This section is intended to give you an overview of common protocol types and the applications that generate them.
If you have located the workstation(s) that is causing the problem but cannot determine which application is causing a problem, you will likely need to examine the packets that are being sent out and determine what application is sending them. Normally you would use an Ethernet monitoring device known as a packet sniffer. We recommend Etherpeek, a full featured Ethernet packet sniffer. This application is designed to display all packets that are transmitted across your LAN and display information about those packets. There is a trial version of Etherpeek on the Netopia CD-ROM in the goodies folder which can normally be used for these purposes.
Etherpeek, if used correctly, will show you the traffic that is destined for the Internet which may be causing the router to dial out. The information that you should be most interested in is the destination source port. This port identifies what type of application the packet is destined for. The common ports are listed below along with their associated application. If the port that you are seeing is not in listed here, then you may need to do more research into what is causing this problem or you may need to have a consultant assess the problems that you are having.
| Application | Port | Protocol Type |
| FTP | 20 or 21 | TCP |
| Web Browser | 80 | TCP |
| NetBIOS | 137, 138 or 139 | UDP and TCP |
| 110 or 25 | TCP | |
| Real Audio | 7070 (Unconfirmed) | UDP and TCP |
| ping | N/A | ICMP |
| News Reader | 119 | TCP |
There are a number of possible causes for unwanted Dial On Demand connections. Careful troubleshooting and detailed detective work will often isolate the exact cause of the problem. First, determine that the LAN is the cause (unplugging the EN cable is the quickest way to do this), and then find out the source and type of traffic by using the WAN event histories and/or a packet capturing software program or hardware device. These steps will often lead to a solution to the problem.