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Understanding IPv6
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.
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.
Neighbor discovery throttling ensures that the switch CPU is not unnecessarily burdened while it is in
the process of obtaining the next hop forwarding information to route an IPv6 packet. The switch
performs a drop in hardware of any additional IPv6 packets whose next hop is the same neighbor the
CPU is actively resolving. Performing this drop avoids adding further load on the CPU and results in a
more efficient use of the switch CPU in an IPv6 routed environment.
IPv6 Stateless Autoconfiguration and Duplicate Address Detection
IPv6 supports two types of autoconfiguration:
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•
The switch supports stateless autoconfiguration to manage link, subnet, and site addressing changes,
such as management of host and mobile IP addresses.
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
35-4
Stateless autoconfiguration where a host autonomously configures its own link-local address, and
booting nodes send router solicitations to request router advertisements for configuring interfaces.
Stateful autoconfiguration using Dynamic Host Configuration Protocol (DHCP) IPv6.
Chapter 35
Configuring IPv6 Host Functions
OL-8915-03
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Troubleshooting
