CLI Reference Guide-R07

Chapter 26 | DHCP Commands (IPv4 and IPv6)
DHCP Client
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Default Setting
None
Command Mode
Privileged Exec
Command Usage
◆ This command starts the DHCPv6 client process if it is not yet running by
submitting requests for configuration information through the specified
interface(s). When DHCPv6 is restarted, the switch may attempt to acquire an IP
address prefix through stateful address auto-configuration. If the router
advertisements have the “other stateful configuration” flag set, the switch may
also attempt to acquire other non-address configuration information (such as a
default gateway or DNS server) when DHCPv6 is restarted.
Prior to submitting a client request to a DHCPv6 server, the switch should be
configured with a link-local address using the ipv6 address autoconfig
command. The state of the Managed Address Configuration flag (M flag) and
Other Stateful Configuration flag (O flag) received in Router Advertisement
messages will determine the information this switch should attempt to acquire
from the DHCPv6 server as described below.
■
Both M and O flags are set to 1:
DHCPv6 is used for both address and other configuration settings.
This combination is known as DHCPv6 stateful, in which a DHCPv6 server
assigns stateful addresses to IPv6 hosts.
■
The M flag is set to 0, and the O flag is set to 1:
DHCPv6 is used only for other configuration settings.
Neighboring routers are configured to advertise non-link-local address
prefixes from which IPv6 hosts derive stateless addresses.
This combination is known as DHCPv6 stateless, in which a DHCPv6 server
does not assign stateful addresses to IPv6 hosts, but does assign stateless
configuration settings.
◆ DHCPv6 clients build a list of servers by sending a solicit message and
collecting advertised message replies. These servers are then ranked based on
their advertised preference value. If the client needs to acquire prefixes from
servers, only servers that have advertised prefixes are considered.
◆ If the rapid commit option has been enabled on the switch using the ipv6 dhcp
client rapid-commit vlan command, and on the DHCPv6 server, message
exchange can be reduced from the normal four step process to a two-step
exchange of only solicit and reply messages.