Defining and Configuring Neighbor Discovery презентация

IPv6 Operations Defining and Configuring Neighbor Discovery

ICMPv6 ICMPv6 is similar to ICMPv4: Provides diagnostic and error messages Used for path MTU discovery

Path MTU Discovery

Maximum Transmission Unit IPv4 MTU >= 68 octets IPv6 MTU >= 1280 octets Path MTU used

IPv6 over Data Link Layers IPv6 is defined for most data link layers: Ethernet PPP FDDI Token Ring HDLC Nonbroadcast multiaccess ATM Frame Relay IEEE 1394

IPv6 over Ethernet IPv6 has a specific Ethernet protocol ID that is different from the protocol ID in IPv4.

Modified EUI-64 Format A modified EUI-64 address is formed by inserting "FFFE" and “complementing” a bit identifying the uniqueness of the MAC address.

Neighbor Discovery Neighbor discovery: Queries for duplicate address detection Determines the link layer address of a neighbor on the same link Finds neighbor routers on link Achieved by using ICMPv6 with IPv6 multicast

Solicited-Node Multicast Address Solicited-node address: Multicast address with a link-local scope Formed by a prefix and the rightmost 24 bits of every unicast and anycast address

Multicast Mapping over Ethernet

Duplicate Address Detection DAD uses neighbor solicitation to verify the existence of an address to be configured.

Neighbor Discovery: Neighbor Solicitation

Neighbor Discovery: Neighbor Solicitation (Cont.) Neighbor Advertisement Message R: router flag, indicates sender is a router S: solicited flag, indicates message sent in response to a neighbor solicitation O: override flag, indicates advertisement should override existing neighbor cache entry

Neighbor Discovery: Autoconfiguration Autoconfiguration Stateless Uses neighbor discovery router advertisements Stateful Uses DHCPv6 service

Neighbor Discovery: Router Advertisements Routers send periodic router advertisements to the all-nodes multicast address.

Neighbor Discovery Parameters

Neighbor Discovery Parameters (Cont.)

Neighbor Discovery: Router Solicitations At boot time, nodes send router solicitations to promptly receive router advertisements.

Stateless Autoconfiguration Router solicitations are sent by booting nodes to request router advertisement for configuring the interfaces.

Renumbering Renumbering is achieved by modifying the router advertisement to announce the old prefix with a short lifetime and the new prefix.

Value of Autoconfiguration IPv6 address autoconfiguration enables “plug-and-play.” Nodes may be deployed without a DHCPv6 server: Mobile devices (phones, PDAs, autos) Home electronics (TVs, DVRs, appliances) Field telemetry (oil pipeline gauges) Autoconfiguration enables massive deployment (millions) of IPv6 nodes.

Cisco IOS Neighbor Discovery Command Syntax

Cisco IOS Command for Overriding the Neighbor Discovery Defaults

Cisco IOS Command for Overriding the Neighbor Discovery Defaults (Cont.)

Cisco IOS Neighbor Discovery Lifetimes

Cisco IOS Network Prefix Renumbering Scenario

Cisco IOS Network Prefix Renumbering Scenario (Cont.)

Summary ICMP messages are used for many IPv6 functions, including path MTU discovery, neighbor discovery, and router discovery. ICMPv6 is an integral part of IPv6 but looks similar to a Layer 4 protocol, much like TCP or UDP. Path MTU is performed by nodes in an effort to determine the largest packet size they can send to a given destination. It is based on a process of sending large packets and listening for ICMPv6 error messages. Neighbor discovery is a critical process that allows neighbors to determine the link-layer address associated with a given IPv6 address. It also allows hosts to receive prefix information to configure a global-scope address and find the default router. Before a node can use an address, it must test it for uniqueness on the link. DAD is a process by which a node with a "tentative" address that it would like to use determines if that address is already in use. Autoconfiguration provides a type of network “plug-and-play,” easily supporting millions of transient nodes and enabling a network environment with support for mobile phones, field sensors, and home appliances. Cisco routers are IPv6-ready and are configured for IPv6 functions on a global and per-interface basis, depending on the function being enabled.