3Com MSR 50 Series Configuration Manual page 662

662 C 46: IP 6 B
HAPTER V ASICS
n
C
ONFIGURATION
Figure 197 Duplicate address detection
Host A
ICMP type = 135
Src = ::
Dst = FF02::1:FF00:1
Data = 2000::1
The DAD procedure is as follows:
1 Node A sends an NS message whose source address is the unassigned address ::
and destination address is the corresponding solicited-node multicast address of
the IPv6 address to be detected. The NS message contains the IPv6 address.
2 If node B uses this IPv6 address, node B returns an NA message. The NA message
contains the IPv6 address of node B.
3 Node A learns that the IPv6 address is being used by node B after receiving the NA
message from node B. Otherwise, node B is not using the IPv6 address and node A
can use it.
Router/prefix discovery and address autoconfiguration
Router/prefix discovery means that a node locates the neighboring routers, and
learns the prefix of the network where the node is located, and other
configuration parameters from the received RA message.
Stateless address autoconfiguration means that a node automatically configures
an IPv6 address according to the information obtained through router/prefix
discovery.
The router/prefix discovery is implemented through RS and RA messages. The
router/prefix discovery procedure is as follows:
1 After started, a node sends an RS message to request the router for the address
prefix and other configuration information for the purpose of autoconfiguration.
2 The router returns an RA message containing information such as prefix
information option and flag bits. (The router also regularly sends an RA message.)
3 The node automatically configures an IPv6 address and other information for its
interface according to the address prefix and other configuration parameters in
the RA message.
In addition to an address prefix, the prefix information option also contains the
■
preferred lifetime and valid lifetime of the address prefix. After receiving a
periodic RA message, the node updates the preferred lifetime and valid lifetime
of the address prefix accordingly.
An automatically generated address is applicable within the valid lifetime and
■
will be removed when the valid lifetime times out.
Host B
2000::1
NS
ICMP type = 136
NA
Src = 2000::1
Dst = FF02::1
Target address = 2000::1