Robert Mills wrote:

> Ron,
>
> My understanding is that ftp uses port 20 to communicate with and port 21
> for transfering data. That is unless the client goes passive when the data
> port, in the range 21 to 1024, is selected by the server.

Backwards.  21 is the command port, opened by the client.  For normal
data transfer, the client selects a port to listen on and notifies the
server via a PORT command.  The server then opens a connection to the
specified port from a SOURCE port of 20.

In PASV (passive) FTP, the connecions are all client-initiated.

If you have a stateful firewall that is unaware of FTP, and blocks
connections to ephemeral ports, it will not allow regular FTP to work,
only passive.

But doesn't sound like you're even getting *that* far.

As for the traceroute anomaly, most traceroutes are done via UDP to a
high-numbered port with a slowly incrementing TTL.  Windows TRACERT uses
ICMP.  This can result in anomalies if there are arbitrary blocks on
ICMP or UDP traffic (neither will work on the last hop if ICMP
unreachables are blocked entirely, as the traceroute TTL-expired will
not make it through, nor will the port unreachable).

Jeff

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