The Cisco ISR 4000 Series router must only allow incoming communications from authorized sources to be routed to authorized destinations.

From Cisco IOS XE Release 3 RTR Security Technical Implementation Guide

Part of SRG-NET-000364-RTR-000109

Associated with: CCI-002403

SV-88815r1_rule The Cisco ISR 4000 Series router must only allow incoming communications from authorized sources to be routed to authorized destinations.

Vulnerability discussion

Unrestricted traffic may contain malicious traffic that poses a threat to an enclave or to other connected networks. Additionally, unrestricted traffic may transit a network, which uses bandwidth and other resources.Traffic can be restricted directly by an ACL (which is a firewall function) or by Policy Routing. Policy Routing is a technique used to make routing decisions based on a number of different criteria other than just the destination network, including source or destination network, source or destination address, source or destination port, protocol, packet size, and packet classification. This overrides the router's normal routing procedures used to control the specific paths of network traffic. It is normally used for traffic engineering, but can also be used to meet security requirements; for example, traffic that is not allowed can be routed to the Null0 or discard interface. Policy Routing can also be used to control which prefixes appear in the routing table.Traffic can be restricted directly by an ACL (which is a firewall function), or by Policy Routing. This requirement is intended to allow network administrators the flexibility to use whatever technique is most effective.

Check content

Review the Cisco ISR 4000 Series router configuration to determine if the router only allows incoming communications from authorized sources to be routed to authorized destinations. The configuration should look similar to the following example: interface GigabitEthernet 0/0/1 description NIPRNet link ip address x.x.x.x 255.255.255.0 ip access-group Authorized_Sources_ACL in ... ip access-list extended Authorized_Sources_ACL deny ip 1.1.1.0 0.0.0.255 any log ... If the Cisco ISR 4000 Series router does not restrict incoming communications to allow only authorized sources and destinations, this is a finding.

Fix text

Configure the Cisco ISR 4000 Series router to only allow incoming communications from authorized sources to be routed to authorized destinations. The configuration would look similar to the example below: interface GigabitEthernet 0/0/1 description NIPRNet link ip address x.x.x.x 255.255.255.0 ip access-group Authorized_Sources_ACL in ... ip access-list extended Authorized_Sources_ACL deny ip 1.1.1.0 0.0.0.255 any log ...

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