The Cisco router must be configured to have Internet Control Message Protocol (ICMP) redirect messages disabled on all external interfaces.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-216567	CISC-RT-000190	SV-216567r856186_rule		Medium

Description
The ICMP supports IP traffic by relaying information about paths, routes, and network conditions. Routers automatically send ICMP messages under a wide variety of conditions. Redirect ICMP messages are commonly used by attackers for network mapping and diagnosis.

STIG	Date
Cisco IOS Router RTR Security Technical Implementation Guide	2022-09-14

Details

Check Text ( C-17802r287085_chk )
Review the router configuration to verify that the no ip redirects command has been configured on all external interfaces as shown in the example below. interface GigabitEthernet0/1 ip address x.x.x.x 255.255.255.0 no ip redirects If ICMP Redirect messages are enabled on any external interfaces, this is a finding.

Fix Text (F-17798r287086_fix)
Disable ICMP redirects on all external interfaces as shown in the example below. R4(config)#int g0/1 R4(config-if)#no ip redirects