DHCP Client Configuration

Overview

Dynamic Host Configuration Protocol (DHCP Dynamic Host Configuration Protocol) protocol is used for assigning dynamic IP addresses to systems on a network. Dynamic addressing allows a system to have an IP address each time it connects to the network. DHCP makes network administration easier by removing the need to manually assign a unique IP address every time a new system is added to the network. It is especially useful to manage mobile users. Once a system is configured to use DHCP, it can be automatically configured on any network that has a DHCP server.

DHCP uses a client-server model, in which the DHCP server centrally manages the IP addresses used in the network. DHCP clients obtain an IP address on lease from the DHCP server.

DHCP Client Configuration for IPv4

Before configuring the DHCP in client, make sure that DHCP server is ready and also dhcpd is running on the server machine.

Figure 25. DHCP sample topology

#configure terminal	Enter Configure mode.
(config)#feature dhcp	Enable the feature dhcp. This will be enabled by default.
(config)#interface xe1	Specify the interface(xe1) to be configured and enter the interface mode.
(config-if)#ip address dhcp	The client requests for the IP address to the server, once it receives the acknowledgment from the server, it assigns the IP address to the interface in which this command is enabled.
(config if)#exit	Exit interface mode.
(config)#commit	Commit the candidate configuration to the running configuration.
(config)#interface eth0	Enter management interface mode.
(config-if)#ip address dhcp	The client requests for the IP address to the server, once it receives the Acknowledgment from the server, it assigns the IP address to the management interface.
(config if)#exit	Exit interface mode.
(config)#commit	Commit the candidate configuration to the running configuration.

Validation Commands

Copy

#show running-config dhcp
interface xe1
 ip address dhcp
!
ip dhcp relay information option
 
#sh ip interface brief
 
Interface            IP-Address      Admin-Status          Link-Status             GMPLS Type
eth0                 10.12.44.20     up                    up                      -
lo                   127.0.0.1       up                    up                      -
lo.4                 127.0.0.1       up                    up                      -
vlan1.1              unassigned      up                    down                    -
xe1/1                2.2.2.3         up                    up                      -
xe1/2                unassigned      down                  down                    -
xe1/3                unassigned      down                  down                    -
xe1/4                unassigned      up                    down                    -
xe2                 *40.40.40.40     up                    down                    -
xe3/1                20.20.30.1      up                    up                      -

DHCP Client Configuration for IPv6

Before configuring the DHCP in client, make sure that DHCP server is ready and also dhcpd is running on the server machine.

Figure 26. DHCP sample topology

#configure terminal	Enter Configure mode.
(config)#feature dhcp	Enable the feature dhcp. This will be enabled by default.
(config)#interface xe1	Specify the interface(xe1) to be configured and enter the interface mode.
(config-if)#ipv6 dhcp client request dns-nameserver	The client request for name-server configured in server
(config-if)#ipv6 dhcp client request domain-search	The client request for domain names with ip
(config-if)#ipv6 dhcp client request ntp-server	The client request for Ntp server details configured in server
(config-if)#ipv6 dhcp client request rapid-commit	Enables rapid commit option
(config-if)#ipv6 dhcp client request vendor-specific-information	The client request for vendor specific information
(config-if)#ipv6 dhcp client duid llt	Set duid type for DHCP Client. Possible values are llt or ll
(config-if)#ipv6 dhcp client dad-wait-time 300	Max time that the client process should wait for the duplicate address detection to complete before initiating DHCP requests. Values range from 1 - 600
(config-if)#ipv6 address dhcp	The client requests for the IP address to the server, once it receives the acknowledgment from the server, it assigns the IP address to the interface in which this command is enabled.
(config if)#exit	Exit interface mode.
(config)#commit	Commit the candidate configuration to the running configuration.
(config)#interface eth0	Enter management interface mode.
(config-if)#ip address dhcp	The client requests for the IP address to the server, once it receives the Acknowledgement from the server, it assigns the IP address to the management interface.
(config if)#exit	Exit interface mode.
(config)#commit	Commit the candidate configuration to the running. configuration

Validation Commands

Copy

OcNOS#show ipv6 interface brief
Interface            IPv6-Address                                      Admin-Sta
tus
ce20                 fe80::eac5:7aff:fe28:a67b                         [up/up]
 
ce21                 fe80::eac5:7aff:fe28:a67c                         [up/down]
 
eth0                 fe80::eac5:7aff:fe8e:c365                         [up/up]
 
                     *3001::1
xe1                  fe80::eac5:7aff:fe28:a66b                         [up/up]
 
 
OcNOS#show ipv6 dhcp vendor-opts
Interface name      vendor-opts
===============     ====================
xe1                 0:0:9:bf:0:1:0:c:48:65:6c:6c:6f:20:77:6f:72:6c:64:21
 
 
OcNOS#show running-config dhcp
interface eth0
 ip address dhcp
!
interface xe1
 ipv6 dhcp client request dns-nameserver
 ipv6 dhcp client request domain-search
 ipv6 dhcp client request ntp-server
 ipv6 dhcp client request rapid-commit
 ipv6 dhcp client request vendor-specific-information
 ipv6 dhcp client duid llt
 ipv6 dhcp client dad-wait-time 300
 ipv6 address dhcp
!
!