SSH hang question

Gert Doering gert at
Sun Nov 10 20:15:39 AEDT 2019


On Sun, Nov 10, 2019 at 06:58:47PM +1100, Darren Tucker wrote:
> One of the failure modes that can behave as you describe is the infamous TCP MTU
> blackhole, wherein a large packet gets fragmented, the 2nd fragment
> gets dropped for
> some reason and the IP packet times out during reassembly.  

I've run into mobile networks recently that drop packets if you change
the QoS flags.  So SSH negotiation works fine, afterwards the client
changes QoS bits to "interactive", and that seems to confuse their
nat gateway...  "ssh $machine $command" worked, so I changed my .ssh/config

host $myjumphost
  # gert, 19.10.19, "wie non-interactive session" - DTAG hakt grad mal
  ipqos cs1

... and it went back to working.

Might or might not be the case here.


"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             gert at

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