I figured I might have three types of problems where network packet monitoring would be helpful: However, the application can see packets headed to the gateway router through my machine’s network adapter, and that should help me diagnose the problem. With Wireshark running on my main work computer, I could see the network interface cards for the machine on which it was running, but I could not monitor interfaces on other machines, including the router. Wireshark watches network traffic and makes a note of all the different packets traveling past the network interfaces. Within seconds after an idle connection dropped, some mysterious force would ask the modem to dial out again.
However, I was puzzled as to why my on-demand router was dialing out on my phone line when I did not appear to have any applications running. Connections are made automatically if required, and if the connection is idle for a specified interval, the router quietly drops the connection and waits for later requests to dial out again. While there is quite a bit of Ethernet traffic on my network between several Windows machines and a Linux server, only a small portion of the traffic is addressed to the gateway, calling for an outside connection. My SMC Barricade 7004AWBR wireless router has an RS-232 port and can control an external modem, which I use for Internet connectivity. The problems I needed to solve were all with a Windows client. The GPL-licensed utility runs under Linux, Unix, Mac OS X, and Windows. The Wireshark network protocol analyzer helped me track down the cause of some strange and unwanted dialup connections. An uncontrolled dial-on-demand router is not. A controlled dial-on-demand router is a convenient tool.
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