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Thread: sequential ports when using passive ftp

Last post 04-21-2009 12:30 PM by qbernard. 4 replies.

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  • 04-14-2009, 7:29 PM

    sequential ports when using passive ftp

    I have just set up a new ftp server. I am fairly new to FTP an I have a question about how ports are assigned when services are requested. I have a port range like 61000 to 64000 prepared in the firewall and in IIS. The FTP is working but I observed that a new port is assigned after every transaction (LIST, Retrieve, Put). Some excerpts are shown below. Is this behavior normal? Why does the port get discarded after every trivial transaction? Will the pool of ports go back to the beginning when the last port is reached? Or will I be denied access when the ports are used up? Thanks for the help.

     

    .227 Entering Passive Mode (62,146,122,12,199,126)

    ...request or transaction

    227 Entering Passive Mode (62,146,122,12,199,127)

    ...request or transaction

     227 Entering Passive Mode (62,146,122,12,199,128)

    ....etc......

  • 04-14-2009, 10:58 PM In reply to

    Re: sequential ports when using passive ftp

    Steve Schofield
    Windows Server MVP - IIS
    http://weblogs.asp.net/steveschofield


    http://www.IISLogs.com
    Log archival solution
    Install, Configure, Forget
  • 04-15-2009, 3:29 AM In reply to

    Re: sequential ports when using passive ftp

    Ya. this is normal as it would start from the lowest port then increase by 1 until it find an available port.

    You sure you ok 61000 to 64000 port range?
    From calculation - 256*199 + 126 = 51070.. so it should br 51000 to 54000 ?

    Cheers,
    Bernard Cheah
  • 04-15-2009, 3:46 PM In reply to

    Re: sequential ports when using passive ftp

    Thanks for noticing my port range...very perceptive..........yeah they are right......i put bogus numbers in the post.

     

    Thanks

  • 04-21-2009, 12:30 PM In reply to

    Re: sequential ports when using passive ftp

    @@ don't try to confuse me :)

    Cheers,
    Bernard Cheah
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