The Cisco perimeter router must be configured to enforce approved authorizations for controlling the flow of information between interconnected networks in accordance with applicable policy.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-96547	CISC-RT-000250	SV-105685r1_rule		Medium

Description
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.

Description

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.

STIG	Date
Cisco IOS Router RTR Security Technical Implementation Guide	2019-07-25

Details

Check Text ( C-95383r1_chk )
Review the router configuration to verify that ACLs are configured to allow or deny traffic for specific source and destination addresses as well as ports and protocols. In the example below, the router is peering BGP with DISN. ICMP echo and echo-reply packets are allowed for troubleshooting connectivity. WWW traffic is permitted inbound to the NIPRNet host-facing web server (x.12.1.22). interface GigabitEthernet0/1 description Link to DISN ip address x.12.1.10 255.255.255.0 ip access-group FILTER_PERIMETER in … … … ip access-list extended FILTER_PERIMETER permit tcp any any established permit tcp host x.12.1.9 host x.12.1.10 eq bgp permit tcp host x.12.1.9 eq bgp host x.12.1.10 permit icmp host x.12.1.9 host x.12.1.10 echo permit icmp host x.12.1.9 host x.12.1.10 echo-reply permit tcp any host x.12.1.22 eq www deny ip any any log-input If the router is not configured to enforce approved authorizations for controlling the flow of information within the network based on organization-defined information flow control policies, this is a finding.

Check Text ( C-95383r1_chk )

Review the router configuration to verify that ACLs are configured to allow or deny traffic for specific source and destination addresses as well as ports and protocols. In the example below, the router is peering BGP with DISN. ICMP echo and echo-reply packets are allowed for troubleshooting connectivity. WWW traffic is permitted inbound to the NIPRNet host-facing web server (x.12.1.22).

interface GigabitEthernet0/1
description Link to DISN
ip address x.12.1.10 255.255.255.0
ip access-group FILTER_PERIMETER in
…
…
…
ip access-list extended FILTER_PERIMETER
permit tcp any any established
permit tcp host x.12.1.9 host x.12.1.10 eq bgp
permit tcp host x.12.1.9 eq bgp host x.12.1.10
permit icmp host x.12.1.9 host x.12.1.10 echo
permit icmp host x.12.1.9 host x.12.1.10 echo-reply
permit tcp any host x.12.1.22 eq www
deny ip any any log-input

If the router is not configured to enforce approved authorizations for controlling the flow of information within the network based on organization-defined information flow control policies, this is a finding.

Fix Text (F-102223r1_fix)
This requirement is not applicable for the DODIN Backbone. Step 1: Configure an ACL to allow or deny traffic for specific source and destination addresses as well as ports and protocols between various subnets as required. The commands used below were used to create the configuration as shown in the check content. R1(config)#ip access-list extended FILTER_PERIMETER R1(config-ext-nacl)#permit tcp any any established R1(config-ext-nacl)#permit tcp host x.12.1.9 host x.12.1.10 eq bgp R1(config-ext-nacl)#permit tcp host x.12.1.9 eq bgp host x.12.1.10 R1(config-ext-nacl)#permit icmp host x.12.1.9 host x.12.1.10 echo R1(config-ext-nacl)#permit icmp host x.12.1.9 host x.12.1.10 echo-reply R1(config-ext-nacl)#permit tcp any host x.12.1.22 eq www R1(config-ext-nacl)#deny ip any any log-input R1(config-ext-nacl)#exit Step 2: Apply the ACL inbound on all applicable interfaces. R2(config)#int g0/0 R1(config-if)#ip access-group FILTER_PERIMETER in

Fix Text (F-102223r1_fix)

This requirement is not applicable for the DODIN Backbone.

Step 1: Configure an ACL to allow or deny traffic for specific source and destination addresses as well as ports and protocols between various subnets as required. The commands used below were used to create the configuration as shown in the check content.

R1(config)#ip access-list extended FILTER_PERIMETER
R1(config-ext-nacl)#permit tcp any any established
R1(config-ext-nacl)#permit tcp host x.12.1.9 host x.12.1.10 eq bgp
R1(config-ext-nacl)#permit tcp host x.12.1.9 eq bgp host x.12.1.10
R1(config-ext-nacl)#permit icmp host x.12.1.9 host x.12.1.10 echo
R1(config-ext-nacl)#permit icmp host x.12.1.9 host x.12.1.10 echo-reply
R1(config-ext-nacl)#permit tcp any host x.12.1.22 eq www
R1(config-ext-nacl)#deny ip any any log-input
R1(config-ext-nacl)#exit

Step 2: Apply the ACL inbound on all applicable interfaces.

R2(config)#int g0/0
R1(config-if)#ip access-group FILTER_PERIMETER in