Technical data
BLADE OS 5.1 Application Guide
BMD00136, November 2009 Chapter 12: IPv6 Host Management
175
Neighbor Discovery
Neighbor Discovery Overview
The switch uses Neighbor Discovery protocol (ND) to gather information about other router and
host nodes, including the IPv6 addresses. Host nodes use ND to configure their interfaces and
perform health detection. ND allows each node to determine the link-layer addresses of neighboring
nodes, and to keep track of each neighbor’s information. A neighboring node is a host or a router
that is linked directly to the switch. The switch supports Neighbor Discovery as described in RFC
2461.
Neighbor Discover messages allow network nodes to exchange information, as follows:
Neighbor Solicitations allow a node to discover information about other nodes.
Neighbor Advertisements are sent in response to Neighbor Solicitations. The Neighbor
Advertisement contains information required by nodes to determine the link-layer address of
the sender, and the sender’s role on the network.
IPv6 hosts use Router Solicitations to discover IPv6 routers. When a router receives a Router
Solicitation, it responds immediately to the host.
Routers uses Router Advertisements to announce its presence on the network, and to
provide its address prefix to neighbor devices. IPv6 hosts listen for Router Advertisements, and
uses the information to build a list of default routers. Each host uses this information to perform
autoconfiguration of IPv6 addresses.
Redirect messages are sent by IPv6 routers to inform hosts of a better first-hop address for a
specific destination. Redirect messages are only sent by routers for unicast traffic, are only
unicast to originating hosts, and are only processed by hosts.
Host vs. Router
Each IPv6 interface can be configured as a router node or a host node, as follows:
A router node’s IP address is configured manually. Router nodes can send Router
Advertisements.
A host node’s IP address is autoconfigured. Host nodes listen for Router Advertisements that
convey information about devices on the network.
Note – All IPv6 interfaces configured on the switch can forward packets, if IP forwarding is
turned on.