Ipv6 Path Mtu Discovery; Ipv6 Transition Technologies - HP 6125XLG Layer 3-Ip Services Configuration Manual

The generated IPv6 address is valid within the valid lifetime and becomes invalid when the valid lifetime
expires.
After the preferred lifetime expires, the node cannot use the generated IPv6 address to establish new
connections, but can receive packets destined for the IPv6 address. The preferred lifetime cannot be
greater than the valid lifetime.
Redirection
Upon receiving a packet from a host, the gateway sends an ICMPv6 Redirect message to inform a better
next hop to the host when the following conditions are met (similar to the ICMP redirection function in
IPv4):
The interface receiving the packet is the same as the interface forwarding the packet.
•
The selected route is not created or modified by an ICMPv6 Redirect message.
•
• The selected route is not a default route on the device.
The forwarded IPv6 packet does not contain the routing extension header.
•

IPv6 path MTU discovery

The links that a packet passes from a source to a destination can have different MTUs, among which the
minimum MTU is the path MTU. If a packet exceeds path MTU, the source end fragments the packet to
reduce the processing pressure on intermediate devices and to use network resources effectively.
A source end uses path MTU discovery to find the path MTU to a destination, as shown in
Figure 58 Path MTU discovery process
1. The source host sends a packet no larger than its MTU to the destination host.
2. If the MTU of a device's output interface is smaller than the packet, the device discards the packet
and returns an ICMPv6 error message containing the interface MTU to the source host.
3. After receiving the ICMPv6 error message, the source host uses the returned MTU to limit the
packet size, performs fragmentation, and sends the packets to the destination host.
4. Step 2 and step 3 are repeated until the destination host receives the packet. In this way, the
source host finds the minimum MTU of all links in the path to the destination host.

IPv6 transition technologies

IPv6 transition technologies enable communication between IPv4 and IPv6 networks. Several IPv6
transition technologies can be used in different environments and periods.
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Figure 58.