Cisco WLC 5520(UCS 220M4) firmware upgrade

[deshmukh]

Hello, 

We have two Cisco WLC 5520 in active-standby role running on Cisco UCS 220M4 blade. We realized we are running 3.0 firmware version on UCS 220M4 and decided to upgrade the firmware from 3.0 to 4.0 using CIMC Upgrade – 8540/5520 WLC

After upgrade, ssh to CIMC management interface fails with the following error: 

"Unable to negotiate a key exchange method"

I have tried using deprecated ciphers but it doesn't work. 

We haven't upgraded our active WLC yet but would like to know if this is bug or some configuration error. 

Any sugesstions?

Thanks,

Andy

[Leo Laohoo]

NOTE:  I always tell people to read the Release Notes because it contains a wealth of useful information about how to upgrade stuff.  The Release Notes for the CIMC, however, is an exception because it DOES NOT CONTAIN ANY USEFUL INFORMATION about how to upgrade the CIMC.  

Have a read of this:  CIMC Upgrade – WLC in HA

[deshmukh]

Thanks for the message. I did read release notes before upgrade and I have read CIMC Upgrade guide you posted before upgrade.

[deshmukh · Accepted solution]

Issue is resolved after upgrading OpenSSH version and/or Putty version. 

Older SSH clients don't support the following: 

One of each of the following category must be supported on the SFTP / SSH Server:
Key exchange algorithms
diffie-hellman-group-exchange-sha256
diffie-hellman-group16-sha512
diffie-hellman-group18-sha512
Encryption algorithms
aes128-ctr
aes192-ctr
aes256-ctr
MAC algorithms
hmac-sha2-256
hmac-sha2-512