3Com Switch 8800 Advanced Software V5 Configuration Guide

226 CHAPTER 23: IPV6 BASICS CONFIGURATION
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CAUTION: The maximum interval for sending RA messages should be less than or
equal to the router lifetime in RA messages.
Configuring the Number
of Attempts to Send an
NS Message for DAD
An interface sends a neighbor solicitation (NS) message for DAD after acquiring an
IPv6 address. If the interface does not receive a response within a specified time
(determined by the ipv6 nd ns retrans-timer command), it continues to send an
NS message. If it still does not receive a response after the number of attempts to
send an NS message reaches the maximum, the acquired address is considered
available.
Follow these steps to configure the attempts to send an NS message for DAD:
Configuring PMTU
Discovery
Configuring the
Interface MTU
IPv6 routing devices do not support packet fragmentation. After an IPv6 routing
device receives an IPv6 packet, if the packet size is greater than the MTU of the
forwarding interface, the device will discard the packet. Meanwhile, the device
sends the MTU to the source host through an ICMPv6 packet - Packet Too Big
message. The source host fragments the packet according to the MTU and resends
it. To reduce the extra flow overhead resulting from packets being discarded, a
proper interface MTU should be configured according to the actual networking
environment.
Follow these steps to configure the interface MTU:
Configuring a Static
PMTU for a Specified
IPv6 Address
You can configure a static PMTU for a specified destination IPv6 address. When a
source host sends packets through an interface, it compares the interface MTU
with the static PMTU of the specified destination IPv6 address. If the packet size is
larger than the smaller one between the two values, the host fragments the
packet according to the smaller value.
Follow these steps to configure a static PMTU for a specified address:
To do... Use the command... Remarks
Enter system view system-view -
Enter interface view interface interface-type
interface-number
-
Configure the number of
attempts to send an NS
message for DAD
ipv6 nd dad attempts value Optional
1 by default. When the value
argument is set to 0, DAD is
disabled.
To do... Use the command... Remarks
Enter system view system-view -
Enter interface view interface interface-type
interface-number
-
Configure the interface MTU ipv6 mtu mtu-size Optional