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


Overview

Finding ID Version Rule ID IA Controls Severity
V-256034 ARST-RT-000550 SV-256034r882444_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
Arista MLS EOS 4.2x Router Security Technical Implementation Guide 2023-01-17

Details

Check Text ( C-59710r882442_chk )
Review the device configuration to determine if controls have been defined to ensure the router does not send ICMP Redirect messages out to any external interfaces.

Step 1: To verify the ACL is configured to determine the router does not send ICMP Redirect messages out to any external interfaces, execute the command "sh ip access-list".

ip access-group DENY_REDIRECT
deny icmp any any redirect
permit ip any any

Step 2: To verify the ACL is applied outbound on interface, execute the command "sh run int Eth YY".

interface Ethernet 2
ip access-group DENY_REDIRECT out

If ICMP Redirect messages are enabled on any external interfaces, this is a finding.
Fix Text (F-59653r882443_fix)
Step 1: Disable ICMP redirects on all external interfaces.

ip access-group DENY_REDIRECT
deny icmp any any redirect
permit ip any any

Step 2: Apply the ACL outbound on interfaces.

interface Ethernet 2
description EXTERNAL INTERFACE
ip access-group DENY_REDIRECT in