The Cisco perimeter switch must be configured to filter egress traffic at the internal interface on an inbound direction.

Access lists are used to separate data traffic into that which it will route (permitted packets) and that which it will not route (denied packets). Secure configuration of switches makes use of access lists to restrict access to services on the switch itself as well as filter traffic passing through the switch.

Inbound versus Outbound: Some operating systems' default access lists are applied to the outbound queue. The more secure solution is to apply the access list to the inbound queue for three reasons:

- The switch can protect itself before damage is inflicted. - The input port is still known and can be filtered on. - It is more efficient to filter packets before routing them.

Review the switch configuration to verify that the egress access control list (ACL) is bound to the internal interface in an inbound direction.

interface interface GigabitEthernet0/2 description downstream link to LAN ip address 10.1.25.5 255.255.255.0 ip access-group EGRESS_FILTER in

If the switch is not configured to filter traffic leaving the network at the internal interface in an inbound direction, this is a finding.

Configure the switch to use an inbound ACL on all internal interfaces as shown in the example below:

SW1(config)#int g0/2 SW1(config-if)#ip access-group EGRESS_FILTER in