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Thread: DSL connection woes

  1. #1
    Mentor jro's Avatar
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    DSL connection woes

    I just moved to a new town and with it came new utilities, one of the most important being my internet connection. I signed up with Verizon, simply because they were pretty much the only available provider in the area. All has been well and good, I even get quite a bit higher than the advertised speeds, but I haven't been able to access any of my machines from the out side.

    From what I have been able to figure out (nmap, netstat,etc..), Verizon completely blocks ALL incoming traffic below port 1024. And it appears they also use some sort of stateful firewall between me and the internet. So only established connections can get back in. I am not totally sure this is the case as I haven't devoted alot of time to figuring it out, but it has bested all of my initial attempts to get in from the out side.

    Really all I want to do is be able to SSH into my machines from outside. Everything else I can just tunnel.

    Anyone have any ideas how to beat this?
    jro - http://jeff.robbins.ws
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  2. #2
    Can't you just configure ssh to run on a higher port?
    My crime is that of curiosity. My crime is that of judging people by what they say and think, not what they look like. My crime is that of outsmarting you, something that you will never forgive.

  3. #3
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    Schotty's Avatar
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    Again, as trickster said, either set it to a new port or do port mapping. Set port 1.2.3.4:20000 to 192.168.0.1:23 or whatever.

    There are a few ways around this.

  4. #4
    Mentor jro's Avatar
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    I tried that, I ran sshd on a number of different ports from 2000 to 60000. All attempts failed. This makes me think that they are running some sort of stateful firewall. Not allowing packets in that aren't part of an already established session, originating from within.

    I will keep trying tho, thanks for the ideas..
    jro - http://jeff.robbins.ws
    Linux counter#:213782
    GnuPG ID: 406238E7

  5. #5
    Mentor jro's Avatar
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    I finally figured out, the modem Verizon sent me acts as a router and firewall too with the default config. So after sifting through all the posts on DSLReports, I finally got everything playing nicely.

    I set the modem set to bridge and let the actual router do the heavy lifing of running the DHCP server and firewall, and, ehm routing. Nmap showed that the ports I opened in the firewall were indeed open to the outside world, and I was able to secure shell in! Victory!! They don't even block port 80 as I was lead to believe they did!

    One thing that _IS_ a bit annoying about the connection is that my external IP is renewed/changed about every 2 to 4 hours. I had to shorten the amount of time between cron jobs that checks for external IP changes and updates ZoneEdit. Now it runs every 30 minutes. Its a great script, but I need to turn down logging.

    So the short story is this: I disabled the DHCP server on the modem, then set it to bridge mode. Then on the router I enabled the DHCP server, set it to PPPoE, entered my creds, cloned the MAC address of the router, and opened the appropriate ports in the firewall. Of course this took me two weeks to figure out this is what needed to happen, and the forums on dslreports.com helped immensely too.
    jro - http://jeff.robbins.ws
    Linux counter#:213782
    GnuPG ID: 406238E7

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