Administrator 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 59. 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.
The DNS server address does not allow the following:
• link local addresses
• loopback addresses
IPv6 Routing
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