Replacing 2 Big IP units

I hope that I understood what you mean exactly and got the right information.

yes, you are right. it is what i want.

The certificate does not match the key. To change them try 'tmsh modify sys httpd { ssl-certfile /etc/httpd/conf/ssl.crt/server.crt ssl-certkeyfile /etc/httpd/conf/ssl.key/server.key }'

it seems httpd's certificate and key do not match. can you correct it? and then re-load configuration (tmsh load sys config).

sol13349: Verifying SSL certificate and key pairs from the command line (11.x)

sol14620: Managing SSL certificates for BIG-IP systems using the Configuration utility