The Cisco router must be configured to have Internet Control Message Protocol (ICMP) mask reply 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. Mask Reply ICMP messages are commonly used by attackers for network mapping and diagnosis.
- ID
- SV-216747r856438_rule
- Version
- CISC-RT-000180
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Disable ipv4 mask-reply 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)#no ipv4 mask-reply