Cisco ASA 5505 Network Port Interfaces

The figure below (taken from Cisco) illustrates the back panel of the Cisco ASA 5505 appliance, showing the network interfaces and other important hardware points.

 Starting from right to left, we have Ethernet0/0 up to Ethernet0/7. The last two Ports 6 and 7 are also Power over Ethernet Ports (PoE), which means that in addition to normal computers, you can also connect IP Phones which will be powered by the firewall PoE ports.

The eight network interfaces of the ASA 5505 work only as Layer 2 ports, which is the difference of the 5505 model from the other ASA models.

This means that you can not configure a Layer 3 IP address directly on each interface. Also, port Ethernet0/0 is used as the Outside untrusted interface (connecting to Internet), and the rest interfaces 0/1 to 0/7 are used as the trusted Inside interfaces connecting to internal hosts.

By default, Vlan 2 is assigned to Ethernet0/0 and the native Vlan 1 is assigned to the rest of the interfaces.

Two Switch Vlan Interfaces (SVI) exist by default (Interface Vlan 1 and Interface Vlan 2) which can be used to assign the Layer 3 IP addresses for the Outside interface (Ethernet 0/0) and for the inside zone (Ethernet0/1 to 0/7).