The Cisco IOS XE router must enforce approved authorizations for controlling the flow of information between interconnected networks in accordance with applicable policy.

From Cisco IOS XE Release 3 RTR Security Technical Implementation Guide

Associated with: CCI-001414

SV-88769r2_rule The Cisco IOS XE router must enforce approved authorizations for controlling the flow of information between interconnected networks in accordance with applicable policy.

Vulnerability discussion

Information flow control regulates authorized information to travel within a network and between interconnected networks. Controlling the flow of network traffic is critical so it does not introduce any unacceptable risk to the network infrastructure or data. An example of a flow control restriction is blocking outside traffic claiming to be from within the organization. For most routers, internal information flow control is a product of system design.

Check content

Review the Cisco IOS XE router configuration. Verify that the external interface blocks inbound traffic with a source IP address belonging to the internal network. The configuration should look similar to the example below where the private IP address space is 1.1.1.0/24: interface FastEthernet 0/0 description NIPRNet link ip address x.x.x.x 255.255.255.0 ip access-group INGRESS_ACL in ... ip access-list extended INGRESS_ACL deny ip 1.1.1.0 0.0.0.255 any log ... If the external interface of the Cisco IOS XE router has not been configured to block all inbound packets with a source IP address belonging to the private network, this is a finding.

Fix text

Configure the Cisco IOS XE router to block all inbound packets with a source IP address belonging to the private network. The configuration would look similar to the example below: interface FastEthernet 0/0 description NIPRNet link ip address x.x.x.x 255.255.255.0 ip access-group INGRESS_ACL in ... ip access-list extended INGRESS_ACL deny ip 1.1.1.0 0.0.0.255 any log ...

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