The Cisco ISR 4000 Series router must not be a BGP peer with a router from an Autonomous System belonging to any Alternate Gateway.

From Cisco IOS XE Release 3 RTR Security Technical Implementation Guide

Associated with: CCI-001414

SV-88783r1_rule The Cisco ISR 4000 Series router must not be a BGP peer with a router from an Autonomous System belonging to any Alternate Gateway.

Vulnerability discussion

The perimeter router will not use a routing protocol to advertise NIPRNet addresses to Alternate Gateways. Most ISPs use Border Gateway Protocol (BGP) to share route information with other autonomous systems, that is, any network under a different administrative control and policy than a local site. If BGP is configured on the perimeter router, no BGP neighbors will be defined to peer routers from an AS belonging to any Alternate Gateway. The only allowable method is a static route to reach the Alternate Gateway.

Check content

Review the configuration of the Cisco ISR 4000 Series router connecting to the Alternate Gateway. Verify there are no BGP neighbors configured to the remote AS that belongs to the Alternate Gateway service provider. If there are BGP neighbors connecting the remote AS of the Alternate Gateway service provider, this is a finding.

Fix text

Configure a static route on the perimeter Cisco ISR 4000 Series router to reach the AS of a router connecting to an Alternate Gateway, using the following command: ISR4000 (config) #ip route The configuration would look similar to the example below: ip route 1.1.1.0 255.255.255.0 2.2.2.2

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