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V-265442

CAT II (Medium)

The NSX Tier-0 Gateway router must be configured to have Internet Control Message Protocol (ICMP) mask replies disabled on all external interfaces.

Rule ID

SV-265442r999916_rule

STIG

VMware NSX 4.x Tier-0 Gateway Router Security Technical Implementation Guide

Version

V1R2

CCIs

CCI-002385

Discussion

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.

Check Content

If the Tier-0 Gateway is deployed in an Active/Active HA mode, this is Not Applicable.

From the NSX Manager web interface, go to Security >> Policy Management >> Gateway Firewall >> Gateway Specific Rules, and choose each Tier-0 Gateway in the drop-down menu.

Review each Tier-0 Gateway Firewall rule to verify one exists to drop ICMP mask replies.

If a rule does not exist to drop ICMP mask replies, this is a finding.

Fix Text

To configure a shared rule to drop ICMP unreachable messages, do the following:

From the NSX Manager web interface, go to Security >> Policy Management >> Gateway Firewall >> All Shared Rules.

Click "Add Rule" (add a policy first if needed). Under "Services", select the custom service that identifies ICMP mask replies, and then click "Apply".

Enable logging, under the "Applied To" field select the target Tier-0 gateways' external interfaces, and then select "Publish" to enforce the new rule.

Note: A rule can also be created under Gateway Specific Rules to meet this requirement.

Note: A pre-created service for ICMP mask replies does not exist by default and may need created.