IPv6 Routing | 453
IPv6 Neighbor Discovery
IPv6 NDP is supported on platforms c e s z
Neighbor Discovery Protocol (NDP) is a top-level protocol for neighbor discovery on an IPv6 network. In
lieu of ARP, NDP uses “Neighbor Solicitation” and “Neighbor Advertisement” ICMPv6 messages for
determining relationships between neighboring nodes. Using these messages, an IPv6 device learns the
link-layer addresses for neighbors known to reside on attached links, quickly purging cached values that
become invalid.
With ARP, each node broadcasts ARP requests on the entire link. This approach causes unnecessary
processing by uninterested nodes. With NDP, each node sends a request only to the intended destination
via a multicast address with the unicast address used as the last 24 bits. Other hosts on the link do not
participate in the process, greatly increasing network bandwidth efficiency.
Figure 21-3. NDP Router Redirect
Note: If a neighboring node does not have an IPv6 address assigned, it must be manually pinged to allow
the IPv6 device to determine the relationship of the neighboring node.
Note: To avoid problems with network discovery, Dell Force10 recommends configuring the static route
last or assigning an IPv6 address to the interface and assigning an address to the peer (the forwarding
router’s address) less than 10 seconds apart.
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