User's Manual

24-27
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 24 Configuring DHCP Features and IP Source Guard
Configuring DHCP Server Port-Based Address Allocation
Enabling DHCP Server Port-Based Address Allocation
Beginning in privileged EXEC mode, follow these steps to globally enable port-based address allocation
and to automatically generate a subscriber identifier on an interface.
After enabling DHCP port-based address allocation on the switch, use the i
p dhcp pool global
configuration command to preassign IP addresses and to associate them to clients. To restrict
assignments from the DHCP pool to preconfigured reservations, you can enter the reserved-only DHCP
pool configuration command. Unreserved addresses that are part of the network or on pool ranges are
not offered to the client, and other clients are not served by the pool. By entering this command, users
can configure a group of switches with DHCP pools that share a common IP subnet and that ignore
requests from clients of other switches.
Beginning in privileged EXEC mode follow these steps to
preassign an IP address and to associate it to
a client identified by the interface name.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip dhcp use subscriber-id client-id Configure the DHCP server to globally use the
subscriber identifier as the client identifier on all
incoming DHCP messages.
Step 3
ip dhcp subscriber-id interface-name Automatically generate a subscriber identifier based
on the short name of the interface.
A subscriber identifier con
figured on a specific
interface takes precedence over this command.
Step 4
interface interface-id Specify the interface to be configured, and enter
interface configuration mode.
Step 5
ip dhcp server use subscriber-id client-id Configure the DHCP server to use the subscriber
identifier as the client identifier on all incoming
DHCP messages on the interface.
Step 6
end Return to privileged EXEC mode.
Step 7
show running config Verify your entries.
Step 8
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip dhcp pool poolname Enter DHCP pool configuration mode, and define the
name for the DHCP pool. The pool name can be a
symbolic string (such as Engineering) or an integer
(such as 0).
Step 3
network network-number [mask | /prefix-length] Specify the subnet network number and mask of the
DHCP address pool.
Step 4
address ip-address client-id string [ascii] Reserve an IP address for a DHCP client identified by
the interface name.
string—can
be an ASCII value or a hexadecimal
value.