CISC-RT-000500 - The Cisco BGP router must be configured to reject inbound route advertisements for any prefixes belonging to the local autonomous system (AS).

Information

Accepting route advertisements belonging to the local AS can result in traffic looping or being black-holed, or at a minimum, using a non-optimized path.

Solution

Configure the router to reject inbound route advertisements for any prefixes belonging to the local AS.

Step 1: Add to the prefix filter list those prefixes belonging to the local autonomous system.

R1(config)#ip prefix-list PREFIX_FILTER seq 74 deny x.13.1.0/24 le 32

Step 2: If not already completed to be compliant with previous requirement, apply the prefix list filter inbound to each external BGP neighbor as shown in the example.

R1(config)#router bgp xx
R1(config-router)#neighbor x.1.1.9 prefix-list PREFIX_FILTER in
R1(config-router)#neighbor x.2.1.7 prefix-list PREFIX_FILTER in

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XE_Router_Y23M10_STIG.zip

Item Details

Category: ACCESS CONTROL

References: 800-53|AC-4, CAT|II, CCI|CCI-001368, Rule-ID|SV-216688r531086_rule, STIG-ID|CISC-RT-000500, STIG-Legacy|SV-106087, STIG-Legacy|V-96949, Vuln-ID|V-216688

Plugin: Cisco

Control ID: af75a2e23e5b96875a9bd54b8ab8b698b49a9cc0a2e32bc313d4897370172bac