[Cyberduck-trac] [Cyberduck] #11663: Transferring a file through SFTP in the LAN w/Cyberduck makes my *Internet* slow

[Cyberduck]

#11663: Transferring a file through SFTP in the LAN w/Cyberduck makes my *Internet*
slow
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    Reporter:  ItalyPaleAle  |      Owner:
        Type:  defect        |     Status:  new
    Priority:  normal        |  Milestone:
   Component:  core          |    Version:  7.8.5
    Severity:  normal        |   Keywords:
Architecture:                |   Platform:  macOS 11
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 This is a really weird issue and I haven't been able to explain it.

 Scenario:
 - I have a small server inside my LAN.
 - My network is fairly simple: everything is connected via switches, and I
 have some UniFi access points for WiFi. The firewall is a pfSense box.
 - I connect to that through Cyberduck to transfer (download/upload) files
 using SFTP
 - While I am transferring files using Cyberduck to that server,
 inexplicably traffic to the public Internet from any other device in the
 home is incredibly slow (to the point when web pages time out before
 they're loaded)
 - However, if I try to connect to another host within the LAN, the
 connection is really fast. So, I can access other resources on the same
 server, or I can connect to other hosts in the LAN (say, my firewall), and
 there's no issue whatsoever. Only connections to the public internet are
 blocked.

 If instead of using Cyberduck I transfer files using `scp` on the command
 line, there's no issue whatsoever on the network, and everything works
 fine.

 I am not sure how to explain it, but it sounds like Cyberduck may be doing
 something that interferes with my network?

 I'm using Cyberduck 7.8.5 on macOS 11.2.3. I'm on a M1 MacBook pro.

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Ticket URL: <https://trac.cyberduck.io/ticket/11663>
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