Linux - NetworkingThis forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.
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I'm having a strange problem with my linux network connection. The box has a 3COM 3c509 card and is sitting on a cable-modem DHCP network. Everything used to work just fine until about three weeks ago, when my ISP made some changes in there network.
Now, when I bring the interface up, it gets and IP address fine - with the gateway, DNS, broadcast, etc. After that, I cannot connect to anything - I cannot even ping the gateway. The ping says "x packets sent, 0 packets received, packet loss 100%" with x anywhere up to several thousand.
The most interesting thing is that I can connect to the box from outside! I can connect to the http server running there, I can log in using SSH, and so on. I don't have any problems connecting using SSH and doing whatever I need to do.
Note that if I connect a windows 2000 machine to the same cable modem, everything works fine.
The ISP is less than helpful - their tech support people basically hang up on me as soon as I say that I use linux, they become very defensive and rude, announce that they only support windows machines, that I'm out of luck and hang up on me. I don't have other alternatives for an ISP, since I live in a rural area where no DSL is available - even from Verizon, who's my telephone carrier.
The greatest thanks to Griffon26 for helping me resolve the problem.
Here's what was wrong. In my firewall/masquarade script, in the beginning, I had the rule
assuming that it would flush all rules in all tables. I was mistaken. Apparently, it did not flush the 'nat' table. Therefore the 'nat' table still had my old IP address stored in it and try to present the packets from my linux box with my old IP address, effectively spoofing the address. The solution was extreamly simply, just like everything great. I replaced the line above with these three lines: