strange network problem - Networking

This is a discussion on strange network problem - Networking ; Hi, I have strange problem with one of my serwer ping works great to certain packet size ping -s 494 s4.my-fantasy.net PING s4.my-fantasy.net (193.218.155.58) 494(522) bytes of data. 502 bytes from 193.218.155.58: icmp_seq=0 ttl=63 time=0.553 ms 502 bytes from 193.218.155.58: ...

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Thread: strange network problem

  1. strange network problem

    Hi,
    I have strange problem with one of my serwer

    ping works great to certain packet size

    ping -s 494 s4.my-fantasy.net
    PING s4.my-fantasy.net (193.218.155.58) 494(522) bytes of data.
    502 bytes from 193.218.155.58: icmp_seq=0 ttl=63 time=0.553 ms
    502 bytes from 193.218.155.58: icmp_seq=1 ttl=63 time=0.647 ms
    502 bytes from 193.218.155.58: icmp_seq=2 ttl=63 time=0.566 ms

    --- s4.my-fantasy.net ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2001ms
    rtt min/avg/max/mdev = 0.553/0.588/0.647/0.050 ms, pipe 2

    but one byte more:

    ping -s 495 s4.my-fantasy.net
    PING s4.my-fantasy.net (193.218.155.58) 495(523) bytes of data.

    --- s4.my-fantasy.net ping statistics ---
    7 packets transmitted, 0 received, 100% packet loss, time 6006ms

    Other services on this machine (eg. HTTP) works only when request
    headers and server reply are shorter than 500 bytes

  2. Re: strange network problem

    On Dec 18, 12:47 pm, "Jacek Zem≥o" wrote:
    > Hi,
    > I have strange problem with one of my serwer
    >
    > ping works great to certain packet size
    >
    > ping -s 494 s4.my-fantasy.net
    > PING s4.my-fantasy.net (193.218.155.58) 494(522) bytes of data.
    > 502 bytes from 193.218.155.58: icmp_seq=0 ttl=63 time=0.553 ms
    > 502 bytes from 193.218.155.58: icmp_seq=1 ttl=63 time=0.647 ms
    > 502 bytes from 193.218.155.58: icmp_seq=2 ttl=63 time=0.566 ms
    >
    > --- s4.my-fantasy.net ping statistics ---
    > 3 packets transmitted, 3 received, 0% packet loss, time 2001ms
    > rtt min/avg/max/mdev = 0.553/0.588/0.647/0.050 ms, pipe 2
    >
    > but one byte more:
    >
    > ping -s 495 s4.my-fantasy.net
    > PING s4.my-fantasy.net (193.218.155.58) 495(523) bytes of data.
    >
    > --- s4.my-fantasy.net ping statistics ---
    > 7 packets transmitted, 0 received, 100% packet loss, time 6006ms
    >
    > Other services on this machine (eg. HTTP) works only when request
    > headers and server reply are shorter than 500 bytes


    Sounds like an MTU is set wrong somewhere.

    DS

  3. Re: strange network problem

    "Jacek Zem≥o" writes:

    > Hi,
    > I have strange problem with one of my serwer
    >
    > ping works great to certain packet size
    >
    > ping -s 494 s4.my-fantasy.net
    > PING s4.my-fantasy.net (193.218.155.58) 494(522) bytes of data.
    > 502 bytes from 193.218.155.58: icmp_seq=0 ttl=63 time=0.553 ms
    > 502 bytes from 193.218.155.58: icmp_seq=1 ttl=63 time=0.647 ms
    > 502 bytes from 193.218.155.58: icmp_seq=2 ttl=63 time=0.566 ms
    >
    > --- s4.my-fantasy.net ping statistics ---
    > 3 packets transmitted, 3 received, 0% packet loss, time 2001ms
    > rtt min/avg/max/mdev = 0.553/0.588/0.647/0.050 ms, pipe 2
    >
    > but one byte more:
    >
    > ping -s 495 s4.my-fantasy.net
    > PING s4.my-fantasy.net (193.218.155.58) 495(523) bytes of data.


    Probably you want to reduce your MTU (Maximum Transmission Unit) size
    down, then. It looks like the full size of the packets is 522 bytes
    (494 bytes of data plus headers), so that's probably about what your
    MTO should be set to. How to do so is OS-specific, but if you post
    the server's OS somebody here will probably know. I see you have
    posted to a Linux newsgroup, so you might want something like:

    ifconfig eth1 mtu 522

    You can play with the numbers a bit to see what works.

    That MTU size seems smaller than I'm used to seeing, and a properly
    configured router should just fragment the packets and send them
    through, so it does seem a little strange.

    Good luck,

    ----Scott.

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