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IPv6 Unicast Routing

ExtremeWare XOS 11.3 Concepts Guide

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Scoped addresses also appear in the outputs of display commands.

IPv6 Addresses Used in Examples

For the purposes of documentation, we follow RFC 3849, which indicates that the prefix 2001:db8::/32

can be used as a global unicast address prefix and will not be assigned to any end party.

Neighbor Discovery Protocol

The Neighbor Discovery Protocol, as defined in RFC 2461, defines mechanisms for the following

functions:

● Resolving link-layer addresses of the IPv6 nodes residing on the link.

● Locating routers residing on the attached link.

● Locating the address prefixes that are located on the attached link.

● Learn link parameters such as the link MTU, or Internet parameters such as the hop limit value that

has to be used in the outgoing packets.

● Automatic configuration of the IPv6 address for an interface.

● Detect whether the address that it wishes to use is not already in use by another node, also known

as Duplicate Address Detection (DAD).

● Redirect the traffic to reach a particular destination through a better first-hop.

MAC Address Resolution

In IPv4, MAC address resolution is done by ARP. For IPv6, this functionality is handled by the

Neighbor Discovery Protocol. The router maintains a cache of IPv6 addresses and their corresponding

MAC addresses and allows the system to respond to requests from other nodes for the MAC address of

the IPv6 Addresses configured on the interfaces. You can also statically configure the MAC Address of

IPv6 destinations on the attached links. Use the following commands to configure, display, and clear the

dynamic Neighbor Discovery cache:

configure neighbor-discovery cache {vr <vr_name>} add [<ipv6address> |

<scoped_link_local>] <mac>

configure neighbor-discovery cache delete {vr <vr_name>} [<ipv6address> |

<scoped_link_local>]

show neighbor-discovery cache ipv6 {[<ipv6_addr> | <mac> | permanent] {vr <vr_name>} |

vlan <vlan_name> | vr <vr_name>}

clear neighbor-discovery cache ipv6 {<ipv6address> {vr <vr_name>} | vlan <vlan_name> |

vr <vr_name>}

Router Discovery

Also supported is router discovery—the ability to send out router advertisements that can be used by a

host to discover the router. The advertisements sent out contain the prefixes and configuration

parameters that allow the end nodes to auto-configure their addresses. The switch also responds to

requests from nodes for router advertisements.

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