I'm having trouble establishing a FTP over explicit TLS connection. The server is set to require SSL. I can establish a connection from machines in the same domain. Machines in a different domain get immediately rejected even before the server asks for a user. The IIS logs show this:

2014-02-14 21:35:32 srcip - dstip 21 ControlChannelOpened - - 0 0 692d5ad2-df2b-404f-8dbd-902b6becc77e - -
2014-02-14 21:35:32 srcip - dstip 21 ControlChannelClosed - - 64 0 692d5ad2-df2b-404f-8dbd-902b6becc77e - -

A ControlChannelOpened followed immediately by a ControlChannelClosed. I use the same Filezilla client from several machines to test. Our network team says it's not a firewall issue. I have also tried passive vs active to no effect.

I also have a packet trace available. Here's the summary:


1 Answer 1


It turns out that a Symantec Web Gateway definitions update blocked all FTP requests.

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