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

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-216746CISC-RT-000170SV-216746r856437_ruleCCI-002385medium
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. Host unreachable ICMP messages are commonly used by attackers for network mapping and diagnosis.
STIGDate
Cisco IOS XR Router RTR Security Technical Implementation Guide2025-08-19

Related Frameworks

1 mapping across 4 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (13) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

MON-01Continuous Monitoring
1.00
MON-01.1Intrusion Detection & Prevention Systems (IDS & IPS)
1.00
MON-01.3Inbound & Outbound Communications Traffic
1.00
MON-01.4System Generated Alerts
1.00
MON-01.8Security Event Monitoring
1.00
NET-01Network Security Controls (NSC)
1.00
NET-02Layered Network Defenses
1.00
SEA-01Secure Engineering Principles
1.00
SEA-02Alignment With Enterprise Architecture
1.00
CAP-01Capacity & Performance Management
0.50

+3 more (top 10 by confidence shown)

NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (36) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AC-10Concurrent Session Control
1.00
AC-17(9)Disconnect or Disable Access
1.00
AC-2(4)Automated Audit Actions
1.00
AC-3Access Enforcement
1.00
AC-4Information Flow Enforcement
1.00
AC-6(9)Log Use of Privileged Functions
1.00
AU-12Audit Record Generation
1.00
AU-3Content of Audit Records
1.00
AU-5Response to Audit Logging Process Failures
1.00
CM-11(2)Software Installation with Privileged Status
1.00

+26 more (top 10 by confidence shown)

CCI1 mapping
CCI-002385
1.00
NIST CSF 2.00 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (3) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

DE.CM-01
1.00
PR.IR-01
1.00
PR.IR-04
0.50

Who does this work

12 NICE work roles and 9 EC-Council certifications.

This is an inference across published mappings, not a single claim by anyone. This check maps to a control, which maps to a Cybersecurity Framework outcome, which NIST assigns to the work roles below. EC-Council separately maps its certifications to those same roles.

A certification prepares someone for a role. It is not evidence that a holder is qualified, and neither NIST nor EC-Council has stated that any certification here addresses this check.

Work-role assignments published by NIST (NICE Framework Components 2.2.0 and the CSF 2.0 OLIR crosswalk). Certification mappings published by EC-Council.

Details

Check Text (C-216746r856437_chk)

Review the configuration to verify the ipv4 unreachables disable command has been configured on all external interfaces as shown in the configuration example below. interface GigabitEthernet0/0/0/1 ipv4 address x.11.1.2 255.255.255.252 ipv4 unreachables disable Note: ICMP unreachables must also be configured. On the Null0 interface if it is used to black hole traffic. If ICMP unreachable notifications are sent from any external or Null0 interface, this is a finding. Alternative – DODIN Backbone Verify that the PE router is configured to rate limit ICMP unreachable messages as shown in the example below. ip icmp ipv4 rate-limit unreachable 60000 ip icmp ipv4 rate-limit unreachable DF 1000 Note: In the example above, packet-too-big message (ICMP Type 3 Code 4) can be sent once every second, while all other destination unreachable messages can be sent once every minute. This will avoid disrupting Path MTU Discovery for traffic traversing the backbone while mitigating the risk of an ICMP unreachable denial of service attack. IF the PE router is not configured to rate limit ICMP unreachable messages, this is a finding.

Fix Text (F-17976r288628_fix)

Disable ip unreachables on all external interfaces as shown below. RP/0/0/CPU0:R3(config)#int g0/0/0/1 RP/0/0/CPU0:R3(config-if)#ipv4 unreachables disable Alternative – DODIN Backbone Configure the PE router to rate limit ICMP unreachable messages as shown in the example below. RP/0/0/CPU0:R3(config)#icmp ipv4 rate-limit unreachable df 1000 RP/0/0/CPU0:R3(config)#icmp ipv4 rate-limit unreachable 60000 RP/0/0/CPU0:R3(config)#end