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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-216657 CISC-RT-000190 SV-216657r531086_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 XE Router RTR Security Technical Implementation Guide 2020-09-23

Details

Check Text ( C-17890r287928_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-17888r287929_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