what is the best way to migrate from Cisco ASA 5520 "ASA version 8.2(1)" firewall to 5525x, iv'e tried to copy the running-config through the CLI and it went horribly " because of the deference in the NAT config and the VPN crypto maps. please advise. regards
Cisco has a guide for migrating your ASA configuration file: Cisco ASA 5500 Migration to Version 8.3
There are also online migration tools which you can find with a quick Google search. I haven't used any so I have no opinion of thm.