Dns For Ipv6; Path Mtu Discovery For Ipv6 Unicast; Icmpv6; Neighbor Discovery - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Understanding IPv6
See the section on IPv6 Unicast Addresses in the "Implementing Basic Connectivity for IPv6" chapter
in the Cisco IOS IPv6 Configuration Library at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t13/ipv6_vgf.htm
Each IPv6 host interface can support up to three addresses in hardware (one aggregatable global unicast
address, one link-local unicast address, and zero or more privacy addresses).

DNS for IPv6

IPv6 introduces new Domain Name System (DNS) record types that are supported in the DNS
name-to-address and address-to-name lookup processes. The new DNS AAAA resource record types
support IPv6 addresses and are equivalent to an A address record in IPv4. The switch supports DNS
resolution for IPv4 and IPv6.

Path MTU Discovery for IPv6 Unicast

The switch supports advertising the system MTU to IPv6 nodes and path MTU discovery. Path MTU
discovery (RFC 1981) allows a host to dynamically discover and adjust to differences in the MTU size
of every link along a given data path. In IPv6, if a link along the path is not large enough to accommodate
the packet size, the source of the packet handles the fragmentation. The switch does not support path
MTU discovery for multicast packets.

ICMPv6

The Internet Control Message Protocol (ICMP) in IPv6 (RFC 2463) functions the same as in IPv4. ICMP
generates error messages, such as ICMP destination unreachable messages, to report errors during
processing and other diagnostic functions. In IPv6, ICMP packets are also used in the neighbor discovery
protocol and path MTU discovery. A value of 58 in the Next Header field of the basic IPv6 packet header
identifies an IPv6 ICMP packet.

Neighbor Discovery

The switch supports Neighbor Discovery Protocol (NDP) for IPv6 (RFC 2461), a protocol running on
top of ICMPv6, and Static Neighbor Discovery for IPv6 stations that do not support NDP. The IPv6
neighbor discovery process uses ICMP messages and solicited-node multicast addresses to determine the
link-layer address of a neighbor on the same network (local link), verify the reachability of the neighbor,
and keep track of neighboring routers.
A value of 135 in the Type field of the ICMP packet header identifies a neighbor solicitation message.
These messages are sent on the local link when a node needs to determine the link-layer address of
another node on the same local link. When a destination node receives a neighbor solicitation message,
it replies by sending a neighbor advertisement message, which has a value of 136 in the ICMP packet
header Type field.
A value of 137 in the ICMP packet header Type field identifies an IPv6 neighbor redirect message. The
switch supports ICMPv6 redirect (RFC 2463) for routes with mask lengths less than 64. ICMP redirect
is not supported for host routes or for summarized routes with mask lengths greater than 64. Routers send
neighbor-redirect messages to inform hosts of better first-hop nodes on the path to a destination. A router
does not update its routing tables after receiving a neighbor-redirect message and hosts do not originate
neighbor-redirect messages.
Catalyst 3750 Switch Software Configuration Guide
36-4
Chapter 36 Configuring IPv6 Unicast Routing
OL-8550-02