Re: sftp ls stalls with certain IP configurations

From: Richard E. Silverman (slade@shore.net)
Date: 02/21/03

  • Next message: Shing-Fat Fred Ma: "Re: Easier alternative to scp?" 
    From: slade@shore.net (Richard E. Silverman)
Date: 20 Feb 2003 23:29:38 -0500

    > Sftp username@(earthlink assigned internal dynamic ip)
    > Type password, type "ls", all still works fine.
    >
    > sftp username@(my dynamic ip as seen from the outside world) (from outside
    > Earthlink, usually from campus -- this external ip is NOT the same as the
    > internal earthlink assigned ip)

    If the address assigned to your machine (by DHCP, PPP, or whatever) is not
    the same as what appears as the source address for connections initiated
    from that machine to elsewhere, then there is a NAT gateway between you
    and the outside world. Some ISP's do this as a matter of course. It's
    evil, because NAT is evil: you are not getting full IP connectivity to the
    Internet for your money. You will not be able to make any connections to
    your machine from elsewhere; you have (limited) outbound connectivity
    only.

    Using the "external dynamic IP" (as you're calling it) on your machine is
    meaningless; that address (if it's even always the same, which is
    unlikely) only corresponds to your machine on the other side of the NAT
    gateway, and only in the context of existing nat'ed network flows (TCP
    connections, UDP query/response pairs, etc.). 

    -- 
  Richard Silverman
  slade@shore.net

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