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ND
The IPv6 Neighbor Discovery (ND) protocol uses ICMPv6 messages to provide the following
functions:
• Address resolution
• Neighbor reachability detection
• DAD
• Router/prefix discovery
• Stateless address autoconfiguration
• Redirection
Table 13 de
scribes the ICMPv6 messages used by ND.
Table 13 ICMPv6 messages used by ND
ICMPv6 message Type Function
Neighbor Solicitation (NS) 135
Acquires the link-layer address of a neighbor.
Verifies whether a neighbor is reachable.
Detects duplicate addresses.
Neighbor Advertisement (NA) 136
Responds to an NS message.
Notifies the neighboring nodes of link layer changes.
Router Solicitation (RS) 133
Requests an address prefix and other configuration
information for autoconfiguration after startup.
Router Advertisement (RA) 134
Responds to an RS message.
Advertises information, such as the Prefix Information
options and flag bits.
Redirect 137
Informs the source host of a better next hop on the path to
a particular destination.
Neighbor entries
A neighbor entry stores information about a neighboring node on the link. Neighbor entries can be
dynamically configured through NS and NA messages or manually configured.
You can configure a static neighbor entry by using one of the following methods:
• Method 1—Associate a neighbor's IPv6 address and link-layer address with the local Layer 3
interface.
If you use Method 1, the device automatically finds the Layer 2 port connected to the neighbor.
• Method 2—Associate a neighbor's IPv6 address and link-layer address with a Layer 2 port in a
VLAN.
If you use Method 2, make sure the corresponding VLAN interface exists and the Layer 2 port
belongs to the VLAN.
RA messages
An RA message is advertised by a router to all hosts on the same link. The RA message contains the
address prefix and other configuration information for the hosts to generate IPv6 addresses through
stateless address autoconfiguration.
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