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 24bits. Other hosts on the link do not participate in the process, greatly increasing network bandwidth efficiency.Figure 57. NDP Router RedirectIPv6 Neighbor Discovery of MTU PacketsYou 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 ndmtu to 1280, the interface still passes 1500-byte packets, if that is what is set with the mtu command.Configuration Task List for IPv6 RDNSSThis section describes how to configure the IPv6 Recursive DNS Server.This sections contains the following configuration task list for IPv6 RDNSS:• Configuring the IPv6 Recursive DNS Server• Debugging IPv6 RDNSS Information Sent to the Host• Displaying IPv6 RDNSS InformationConfiguring the IPv6 Recursive DNS ServerYou 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 lifetimerange is 0 to 4294967295 seconds. When the maximum lifetime value, 4294967295, or the infinite keyword is specified, thelifetime to use the RDNSS address does not expire. A value of 0 indicates to the host that the RDNSS address should not be used. Youmust specify a lifetime using the lifetime or infinite parameter.IPv6 Routing 459
