Developers Guide

IPv6 Neighbor Discovery
The IPv6 neighbor discovery protocol (NDP) is a top-level protocol for neighbor discovery on an IPv6 network.
In place of address resolution protocol (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.
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 EMC Networking 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.
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 57. NDP Router Redirect
IPv6 Neighbor Discovery of MTU Packets
You can set the MTU advertised through the RA packets to incoming routers, without altering the actual MTU setting on the
interface.
The ipv6 nd mtu command sets the value advertised to routers. It does not set the actual MTU rate. For example, if you set
ipv6 nd mtu to 1280, the interface still passes 1500-byte packets, if that is what is set with the mtu command.
Configuring the IPv6 Recursive DNS Server
You can configure up to four Recursive DNS Server (RDNSS) addresses to be distributed via IPv6 router advertisements
to an IPv6 device, using the ipv6 nd dns-server ipv6-RDNSS-address {lifetime | infinite} command in
INTERFACE CONFIG mode.
The lifetime parameter configures the amount of time the IPv6 host can use the IPv6 RDNSS address for name resolution. The
lifetime range is 0 to 4294967295 seconds. When the maximum lifetime value, 4294967295, or the infinite keyword is
specified, the lifetime to use the RDNSS address does not expire. A value of 0 indicates to the host that the RDNSS address
should not be used. You must specify a lifetime using the lifetime or infinite parameter.
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IPv6 Routing