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Greetings All: I run a linux box that hosts a web and game server. The URL is www.teamcqb.net . The game server is running on port 27015. There are 2 ...
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  1. #1
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    Exclamation Server Resources - Some Cannot Access?


    Greetings All:

    I run a linux box that hosts a web and game server. The URL is www.teamcqb.net. The game server is running on port 27015. There are 2 team members that cannot access the homepage or game server or any other resources. It seems like they are being blocked by their ISP (comcast, rr - soon to be comcast), or something else is blocking them. Most of us can hit it just fine, so I do not believe it has anything to do with the server. Having said that, I have been running ping plotters (from their machines) and tcpdump commands on the server to see where the link dies and I just cannot seem to figure it out. They can ping the server and run traceroute. I tested tcpdump one day on several of the open ports and this is what I am seeing:

    This is from a client that can access the server:

    00:11:03.436327 IP (tos 0x20, ttl 114, id 22077, offset 0, flags [DF], proto 6, length: 40) c-**-**-***-*.****.**.comcast.net.1464 > ********.comcast.net.http: . [tcp sum ok] ack 30241 win 65520
    0x0000: 4520 0028 563d 4000 7206 8ece 443a cb03 E..(V=@.r...D:..
    0x0010: 0a01 0a66 05b8 0050 5081 cb68 9e1a e97a ...f...PP..h...z
    0x0020: 5010 fff0 e2b7 0000 0000 0000 0000 P.............
    00:11:03.461096 IP (tos 0x20, ttl 114, id 60184, offset 0, flags [DF], proto 6, length: 40) c-**-**-***-*.****.**.comcast.net.1464 > ********.comcast.net.http: . [tcp sum ok] ack 32517 win 65520
    0x0000: 4520 0028 eb18 4000 7206 f9f2 443a cb03 E..(..@.r...D:..
    0x0010: 0a01 0a66 05b8 0050 5081 cb68 9e1a f25e ...f...PP..h...^
    0x0020: 5010 fff0 d9d3 0000 0000 0000 0000 P.............

    and this is from one the clients that cannot access the server:

    00:14:17.958388 IP (tos 0x20, ttl 112, id 27327, offset 0, flags [DF], proto 6, length: 4 ***.***.***.**.***.***.rr.com.1677 > ********.comcast.net.http: S [tcp sum ok] 899159666:899159666(0) win 65535 <mss 1460,nop,nop,sackOK>
    0x0000: 4520 0030 6abf 4000 7006 8d33 4679 b7d5 E..0j.@.p..3Fy..
    0x0010: 0a01 0a66 068d 0050 3598 1672 0000 0000 ...f...P5..r....
    0x0020: 7002 ffff 1d83 0000 0204 05b4 0101 0402 p...............
    00:14:23.968938 IP (tos 0x20, ttl 112, id 27329, offset 0, flags [DF], proto 6, length: 4 ***.***.***.**.***.***.rr.com.1677 > ********.comcast.net.http: S [tcp sum ok] 899159666:899159666(0) win 65535 <mss 1460,nop,nop,sackOK>
    0x0000: 4520 0030 6ac1 4000 7006 8d31 4679 b7d5 E..0j.@.p..1Fy..
    0x0010: 0a01 0a66 068d 0050 3598 1672 0000 0000 ...f...P5..r....
    0x0020: 7002 ffff 1d83 0000 0204 05b4 0101 0402 p...............

    Their traffic is showing up (I think), but not near as much as one that can hit the server. I do not know enough about tcpdump to understand if the traffic is actually making it to my server or being cut off before. Can someone help me decipher this tcpdump output? Will this tell us if the client is actually making it to the server?

    Thanks in advance for your assistance.

  2. #2
    Just Joined! forgottentq's Avatar
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    try this:

    tcpdump -n -e -t -f -O -q -i eth1

    eth1 being your interface of course.

  3. #3
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    I'll run that just to see what it does, but it looks like we found the solution. His router was cloning his MAC addresses, which for some reason caused my server to not let him in. Not sure why though, I also had cloned my MAC's and it worked fine. I do not believe the firewall blocked his access, because when I turned it off, he still couldn't get in. Makes me wonder what blocked him...Any ideas?

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