Router advertisements must be suppressed on all external-facing IPv6-enabled interfaces.

From Perimeter L3 Switch Security Technical Implementation Guide

Part of IPv6 Router Advertisements must be suppressed.

Associated with IA controls: ECSC-1, DCBP-1

SV-15262r3_rule Router advertisements must be suppressed on all external-facing IPv6-enabled interfaces.

Vulnerability discussion

Many of the known attacks in stateless autoconfiguration are defined in RFC 3756 were present in IPv4 ARP attacks. IPSec AH was originally suggested as mitigation for the link local attacks, but has since been found to have bootstrapping problems and to be very administrative intensive. Due to first requiring an IP address in order to set up the IPSec security association creates the chicken-before-the-egg dilemma. There are solutions being developed (Secure Neighbor Discovery and Cryptographic Generated Addressing) to secure these threats but are not currently available at the time of this writing. To mitigate these vulnerabilities, links that have no hosts connected such as the interface connecting to external gateways will be configured to suppress router advertisements.Disable (or do not configure) all IPv6 Neighbor Discovery functions across tunnels including the Neighbor Unreachability Detection (NUD) function. Note: this is applicable only when the inner IP layer is IPv6 since IPv4 does not have the Neighbor Discovery functionality.

Check content

Inspect the device configuration to validate IPv6 router advertisement suppression is enabled on all external-facing interfaces. This is applicable to all IPv6-enabled interfaces connected to an IP backbone (i.e. NIPRNet, SIPRNet, etc.), backdoor link, or an alternate gateway (AG). If router advertisements are not suppressed on external facing IPv6 interfaces, this is a finding.

Fix text

Configure the network device to enable route advertisement suppression on all external facing have IPv6 enabled on the interface.

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