The Cisco router must be configured to have Internet Control Message Protocol (ICMP) unreachable messages disabled on all external interfaces.
An XCCDF Rule
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.
- ID
- SV-216746r856437_rule
- Version
- CISC-RT-000170
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
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