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New Member

XR 5.1.1 and Putty

I'm having (repeatable) trouble SSH'ing into a ASR9001 running v5.1.1 using PuTTY (6.3).

Anyone else?  

I've been using PuTTY for years without seeing this issue, so I'm thinking 5.1.1 may be acting differently.


I can make the session fail easily by logging in and spacing through a 'show run'.

It always fails with the connection breaking part way through the listing with 

"Disconnected: Server protocol violation: unexpected SSH2_MSG_CHANNEL_FAILURE packet"


The same PuTTY client works fine into ASR9001s running  4.2.3/4.3.0.

I can connect without issue using a linux OpenSSH (4.3p2) or Windows TeraTerm (4.8.1) SSH as clients,

it's just this PuTTY-v5.1.1 combination that seems to cause a problem.


PuTTY uses: AES256-CBC and HMAC-SHA1

TeraTerm also uses: AES256-CBC HMAC-SHA1

OpenSSH uses: AES-128 HMAC-MD5


fwiw, my ASR vty and ssh config is the same on 5.1.1 as it is for previous revs.   

Everyone's tags (1)
Cisco Employee

hi gary,aha interesting, I

hi gary,

aha interesting, I think I know what is going on, this may be a bug in the ssh code that putty "exploits".

can you file a tac case for me and collect the debug ssh messages for this also when this problem is occurring as that is necessary for us to fix the ssh issue.

Can you also try to set the term len to 0 and see if the issue still occurs?

there is a control messaging issue here and based on the details of the debugs and the term len 0 it will point us in the right direction.




Xander Thuijs CCIE #6775 Principal Engineer ASR9000, CRS, NCS6000 & IOS-XR
New Member

Xander,With your thought and


With your thought and gathering a PuTTY debug, I believe I've found it.

In the debug I saw this occuring:   (SSH2_MSG_CHANNEL_WINDOW_ADJUST)

I had to change the following setting within PuTTY. Once set, the connection does not drop.

Change the following session parameter from the default of 'Auto' to 'On'.

Connection...SSH...Bugs...'Chokes on PuTTYs SSH2 winadj request'

FWIW, setting to 'On'  does not seem to negatively impact sessions that were working beforehand.










New Member

Thank you - The solution was

Thank you - The solution was spot on.

Thank you. Works for me.

Thank you. Worked for me.



New Member

This is CSCup31447

This is CSCup31447

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