NET0921 - Bind egress filters to correct interface

Information

The administrator must bind the egress ACL filtering packets leaving the network to 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 routers makes use of access lists for restricting access to services on the router itself as well as for filtering traffic passing through the router. Inbound versus Outbound; it should be noted that 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 3 reasons-

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

NOTE: Change 'INTERNAL_INTERFACE' to the Internal interface for your organization.
NOTE: Change 'INTERNAL_EGRESS_ACL' to the access-list IP standard access list number for your organization.

Solution

Bind the ingress ACL to the external interface (inbound) and the egress ACL to the internal interface (inbound).

See Also

https://iasecontent.disa.mil/stigs/zip/U_Network_Perimeter_Router_L3_Switch_V8R32_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7(11), CAT|II, Rule-ID|SV-15380r2_rule, STIG-ID|NET0921, Vuln-ID|V-14688

Plugin: Cisco

Control ID: af9b710f711d00ddd737636310b6d28e60e049d997541aa64fe76a6027bce218