Understanding Logical Interfaces
Your Security Appliance has a limited number of physical interfaces. This limits the number
of Layer 3 networks to which the Security Appliance can be directly connected. If you use
VLANs to segment your network into smaller broadcast domains, each of these VLANs
represents a different Layer 3 network. By using logical interfaces, you can accommodate
multiple VLANs by using trunk lines on your switch ports and configuring multiple logical
interfaces on a single physical interface on your Security Appliance. Logical interfaces
overcome the physical interface limitation by enabling a single physical interface to handle
multiple logical interfaces.
Table 11-2 shows the maximum number of interfaces allowed using a PIX Firewall restricted
license, while Table 11-3 shows the maximum number of interfaces allowed for a PIX
Firewall unrestricted license.
Table 11-4 shows the maximum number of interfaces allowed using an ASA Security
Appliance base license, while Table 11-5 shows the maximum number of interfaces allowed
for an ASA Security Appliance Security Plus license.