Personally I would not recommend outside interface reconfig as sec level of 100 for accomplishing simple telnet access via outside interface, unless you have the firewall in a LAB and want to experiment with firewall then is fine. Changes to sec level on an already configured firewall with rules will impact ACLs and firewall behaviour when sec levels are changed specially rules bound to outside interface.
The easiest way to access outside interface is through ssh as Sundar provided link shows, it is very easy to do, you will not run into problems as it would by changing sec levels back and forth.
Login to the FXOS chassis manager.
Direct your browser to https://hostname/, and log-in using the user-name and password.
Go to Help > About and check the current version:
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We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...