Overview

The IPv6 ND protocol provides many functions, such as address resolution, neighbor reachability detection, duplicate address detection, router/prefix discovery and address auto-configuration, and redirection. However, it does not provide security mechanisms. Attackers can easily exploit the ND protocol to attack hosts and gateways by sending forged packets. For more information about ND, see Layer 3—IP Services Configuration Guide.

ND uses the following types of ICMPv6 messages:

• Neighbor Solicitation (NS)

• Neighbor Advertisement (NA)

• Router Solicitation (RS)

• Router Advertisement (RA)

• Redirect (RR)

An attacker can attack a network by sending forged ICMPv6 messages, as shown in Figure 122:

• Sending forged NS/NA/RS packets with the IPv6 address of a victim host. The gateway and other hosts update the ND entry for the victim host with incorrect address information. As a result, all packets intended for the victim host go instead to the attacking host.

• Sending forged RA packets with the IPv6 address of a victim gateway. As a result, all hosts attached to the victim gateway maintain incorrect IPv6 configuration parameters and ND entries.

All forged ND packets have these common features:

• The Ethernet frame header and the source link layer address option of the ND packet contain different source MAC addresses.

• The mapping between the source IPv6 address and the source MAC address in the Ethernet frame header is invalid.

The source MAC consistency check and ND detection features can identify forged ND packets.