[c-nsp] putty SSH errors on IOS-XR 5.1.1

Lukas Tribus luky-37 at hotmail.com
Thu Aug 6 05:12:20 EDT 2015


>> Hello,
>> I've got a pair of new ASR-9904 routers running IOS-XR 5.1.1
>> When a lot of data is being sent at once from the router to my client,
>> putty will disconnect and give me the error: "Disconnected: Server
>> protocol violation: unexpected SSH2_MSG_CHANNEL_FAILURE packet".
> Hi Vinny,
> On PuTTY go to:
> Configuration -> Connection -> SSH -> Bugs
> And set “Chokes on PuTTY’s SSH-2 ‘windadj’ requests” to On (the default
> is Auto).

Full disclosure: this is CSCup31447, IOS XR's ssh server erroneously
disconnects the TCP session after sending SSH_MSG_CHANNEL_FAILURE.

Its pretty obvious that the SSH server is not supposed to do that, but
because its not explicitly prohibited in the RFC, the developers seem
unwilling to fix this (quote "It could be a simple fix from our side [...]
but bringing this change will impact the behavior which we exhibited for
long years").




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