CISC-RT-000330 - The Cisco perimeter router must be configured to filter ingress traffic at the external interface on an inbound direction.

Information

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 three 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: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

This requirement is not applicable for the DODIN Backbone.

Configure the router to use an inbound ACL on all external interfaces as shown in the example below.

R1(config)#int g0/2
R1(config-if)#ip access-group EXTERNAL_ACL_INBOUND in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS_Router_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-7a., CAT|II, CCI|CCI-001097, Rule-ID|SV-216581r531085_rule, STIG-ID|CISC-RT-000330, STIG-Legacy|SV-105701, STIG-Legacy|V-96563, Vuln-ID|V-216581

Plugin: Cisco

Control ID: 905b6218f8ce442518910172b7aff5040daa895aa7c32754a83dbbe8c7cffae7