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Network troubleshooting forYou have checked that the equipment is in working order and everthing is connected correctly. Right? Of course!
After boot-up you can check all the messages for something obviously wrong using Shift-PGUP and Shift-PGDN on the Coyote Linux/BrazilFW console. Something like a bad sector on the floppy or an I/O error reading this or that module would do it. NICs are a common cause. Use common sense. If it looks obviously wrong then it probably is wrong.
Note: not all the console messages get recorded to the Kernel Boot Messages displayed by the Diagnostic Tools of BrazilFW Webadmin.
When using a DHCP configuration make sure your modem is not DHCP enabled. I doubt that a ISP would provide such a modem but if you bought your own then it is something to check if you are having problems getting Internet connectivity.How do you know the modem is DHCP enabled? Use the web interface provided or connect it to a Windows PC that is configured to get an address automatically. If it gets an address in the ranges 10.n.n.n, 176.16.n.n through 176.31.n.n or 192.168.n.n then it is DHCP enabled otherwise it will get a Microsoft IP like 169.254.243.n.
Using 2 identical NICs and are having problems? You could have the WAN/LAN cables mixed. Try swaping them. DHCP, PPPoE, and Static configurations can have this problem. The symptoms would be no Internet and no connection to Coyote Linux/Brazil Firewall using either ping or the WebAdmin tool.One way to determine this is to disconnect the wire connected to the modem. For a standard BrazilFW/Coyote Linux installation a message should appear on the console that eth1 is down. If it says eth0, you have them flipped.
Telephone dial-up (PPP) diagnostics are on my dial-up services page.
The examples below use some ISA NICs and ISA is a bit out of date but the techniques and logic used to determine the problem and solution are still valid. Diagnostics 101 and Diagnostics 102 have a badly configured NIC on the LAN side so it is impossible to use the WebAdmin tool. Of course this is on purpose. Diagnostics 103 has a series of errors from a bad WAN configuration to a bad userid/password.
Diagnostics 101 A 3c509 NIC for the LAN and an 8139too for the WANA lot of writers mask out MACs addresses for "security reasons". So now you will know some of my MACs. Big deal!
All tests were conducted in a controlled environment to produce these problems.
DISCLAIMER: The following instructions come with no warranty. Use at your discretion and risks. I am not responsible for its misuse, damages, or losses that can be caused directly or indirectly. It is assumed that you practice safe computing and take backups before making changes.
Stuff is written here for the uninitiated and no prior knowledge on the subject is presumed.
Use the Forums for support so everyone can share the information.
copyright for the writing. The ideas and code are free. Robert Bonomo