The Cisco perimeter switch must be configured to only allow incoming communications from authorized sources to be routed to authorized destinations.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-101627	CISC-RT-000260	SV-110731r1_rule		Medium

Description
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 access control list (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 switch'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. This requirement is intended to allow network administrators the flexibility to use whatever technique is most effective.

Description

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 access control list (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 switch'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. This requirement is intended to allow network administrators the flexibility to use whatever technique is most effective.

STIG	Date
Cisco IOS Switch RTR Security Technical Implementation Guide	2020-05-20

Details

Check Text ( C-100513r1_chk )
Review the switch configuration to determine if the switch allows only incoming communications from authorized sources to be routed to authorized destinations. The hypothetical example below allows inbound NTP from server x.1.12.9 only to host x.12.1.21. ip access-list extended FILTER_PERIMETER permit tcp any any established … … … permit udp host x.12.1.9 host x.12.1.21 eq ntp deny ip any any log-input If the switch does not restrict incoming communications to allow only authorized sources and destinations, this is a finding.

Check Text ( C-100513r1_chk )

Review the switch configuration to determine if the switch allows only incoming communications from authorized sources to be routed to authorized destinations. The hypothetical example below allows inbound NTP from server x.1.12.9 only to host x.12.1.21.

ip access-list extended FILTER_PERIMETER
permit tcp any any established
…
…
…
permit udp host x.12.1.9 host x.12.1.21 eq ntp
deny ip any any log-input

If the switch does not restrict incoming communications to allow only authorized sources and destinations, this is a finding.

Fix Text (F-107311r1_fix)
Configure the switch to allow only incoming communications from authorized sources to be routed to authorized destinations. SW1(config)#ip access-list extended FILTER_PERIMETER SW1(config-ext-nacl)#permit udp host x.12.1.9 host x.12.1.21 eq ntp SW1(config-ext-nacl)#end