When adding a Cisco ASA 5505 firewall to a server that previously ran without it, you must re-map its website IP addresses. When the firewall is installed, it inherits the server's public IP addresses. The server runs on private IP addresses and communicates to the outside through the firewall. Private IP addresses start at 10.0.0.1 and subsequent addresses are created by incrementally increasing the last octet: 10.0.0.2, 10.0.0.3, etc.
The firewall is responsible for statically translating public IP addresses to private IP addresses. For example, a Cisco ASA 5505 firewall added to a server with public IP addresses 220.127.116.11 and 18.104.22.168 inherits these addresses and translates them to private IP addresses 10.0.0.1 and 10.0.0.2, respectively. This process is known as Network Address Translation (NAT).
When the Cisco ASA 5505 hardware firewall is added to an existing server, the translation rules are automatically configured. For information on configuring the rules for new IP addresses, see Configuring Cisco ASA 5505 Firewall NAT Rules and Interfaces.
The use of a hosting control panel such as Plesk or Simple Control Panel may result in issues after hardware firewall installation.
To resolve Simple Control Panel issues, see Using Simple Control Panel with Cisco ASA 5505 Hardware Firewalls.