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SSH into Cisco switch with a new IOS-XE version

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(@itscottw)
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Joined: 6 months ago
Posts: 1
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I am having difficulty using Absolute Telnet version 11.38 to SSH into a Cisco switch running a newer IOS-XE version. When I first attempted to connect Absolute Telnet reported ""disconnected: failed to negotiate client to server MAC algorithm". I then updated the switch to allow hmac-sha2-512. This initially appears to work as I am then prompted for login credentials which is successful.

However, immediately after authenticating I receive a "Remote Server Disconnected Unexpectedly" message. The switch logging shows this error associated with my attempt: "%SSH-3-BAD_PACK_LEN: Bad packet length 1081710372"

I have tried various combinations of encryption and mac settings on both Absolute Telnet and on the Cisco switch but can't seem to get past this bad packet length error. I am able to use other clients, such as Putty, to connect.

Does anyone have any suggestions on how to get past this?

Thanks in advance.


   
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(@bpence)
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Joined: 6 months ago
Posts: 1398
 

Do you get the error even if authentication fails? Or only when in succeeds? For example, if you type in the wrong password, does it fail with the same error, or only fails with a valid password?

There is a new version with quite a few fixes. Let's try that first and see if that helps....

http://www.celestialsoftware.net/telnet/AbsoluteTelnet11.39.exe

If this doesn't help, I may need some more details to track this down.

Brian


   
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(@bpence)
Member Admin
Joined: 6 months ago
Posts: 1398
 

After a few debug sessions with Scott, we determined that there's an interoperability problem between this version of Cisco IOS and Absolute 11.39 and earlier. Cisco is choking on some extra SSH_MSG_IGNORE packets that Absolute sends between other packets.

Absolute 11.41 addresses this issue and is now posted to the download site.

Brian


   
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