ECS4660-28F_Management Guide-R03

C HAPTER 48 | DHCP Commands
DHCP Relay
– 1630 –
◆ You must specify the IP address for at least one active DHCP server.
Otherwise, the switch’s DHCP relay agent will not be able to forward
client requests to a DHCP server. Up to five DHCP servers can be
specified in order of preference.
◆ If any of the specified DHCP server addresses are not located in the
same network segment with this switch, use the ip default-gateway or
ipv6 default-gateway command to specify the default router through
which this switch can reach other IP subnetworks.
◆ To start DHCP relay service, enter the ip dhcp restart relay command.
EXAMPLE
Console(config)#interface vlan 1
Console(config-if)#ip dhcp relay server 10.1.0.99
Console(config-if)#
ip dhcp restart relay This command enables DHCP relay for the specified VLAN. Use the no form
to disable it.
DEFAULT SETTING
Disabled
COMMAND MODE
Privileged Exec
COMMAND USAGE
This command is used to configure DHCP relay functions for host devices
attached to the switch. If DHCP relay service is enabled, and this switch
sees a DHCP request broadcast, it inserts its own IP address into the
request so the DHCP server will know the subnet where the client is
located. Then, the switch forwards the packet to the DHCP server on
another network. When the server receives the DHCP request, it allocates a
free IP address for the DHCP client from its defined scope for the DHCP
client’s subnet, and sends a DHCP response back to the DHCP relay agent
(i.e., this switch). This switch then broadcasts the DHCP response received
from the server to the client.
EXAMPLE
In the following example, the device is reassigned the same address.
Console#ip dhcp restart relay
Console#show ip interface
VLAN 1 is Administrative Up - Link Up
Address is 00-00-0C-00-00-FD
Index: 1001, MTU: 1500
Address Mode is DHCP
IP Address: 192.168.0.3 Mask: 255.255.255.0
Proxy ARP is disabled
Console#