Huawei AR150 series Configuration Manual page 65

Huawei AR150&200 Series Enterprise Routers
Configuration Guide - IP Service
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Selection of Source and Destination Addresses
When network administrators need to specify or plan a source and a destination addresses, they
can define a group of address selection rules. An address selection policy table can be created
based on these rules. Similar to a routing table, this table can be queried based on the longest
match rule. The address is selected based on a source and a destination addresses.
IPv6 Neighbor Discovery
The IPv6 neighbor discovery (ND) is a group of messages and processes that define the
relationship between neighboring nodes. ND replaces the Address Resolution Protocol (ARP)
messages and the Internet Control Message Protocol (ICMP) device discovery messages. It also
provides additional functions.
IPv6 PMTU
Generally, the problem that different networks have different Maximum Transmission Units
(MTU) can be solved in the following ways:
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The Path MTU (PMTU) Discovery mechanism aims at finding a proper MTU value on the path
from the source to the destination.
IPv6 FIB
Connecting network topologies of different types needs the configuration of different routing
protocols. This brings about Routing Information Base (RIB). The RIB is a base of the
Forwarding Information Base (FIB). Guided by route management policies, a device extracts a
minimum of necessary forwarding information from RIB and adds the information to the FIB.
Through the route management module, you can also add static routes into the FIB.
A FIB contains a group of minimum information needed by a device during packet forwarding.
An FIB entry usually contains the destination address, prefix length, transport port, next-hop
address, route flag, and time stamp. A device forwards packets according to FIB entries.
The FIB mechanism consists of two parts: FIB agent (used on the control plane) and FIB
container (used on the forwarding plane). A FIB agent is responsible for interacting with the
RM module for delivering FIB entries to the forwarding engine, and to the I/O board in a
distributed system.
A FIB contains the following information:
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Network prefix: equals the network ID of an IPv4 address. It is of n bits.
Interface identifier: equals the host ID in an IPv4 address. It is of 128-n bits.
Devices fragment packets as required. The source host only needs to fragment packets;
however, the intermediate router not only needs to fragment packets, but also to reassemble
packets.
The source host sends packets based on a proper MTU so that packets need not be
fragmented on the intermediate router. In such a case, packet processing burden on the
intermediate router can be reduced. During IPv6 packet transmission, only this way can be
adopted because IPv6 intermediate routers do not support packet fragmentation.
Destination address: indicates the network or host a packet is destined for.
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3 Basic IPv6 Configuration
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