100
converts them to unicast (with a destination MAC/IP address of the configured DHCP server,
source MAC/IP of the router itself). The field identified as the GIADDR in the main DHCP page
is populated with the IP address of the interface on the router it received the DHCP request on.
The DHCP server uses the
GIADDR
field to identify the subnet the device and select an IP
address from the correct pool. The DHCP server then sends the DHCP OFFER back to the router
via unicast which then converts it back to a broadcast and out to the correct subnet containing
the device requesting an address.
Configurations:
Users can enable/disable the DHCP Relay on the Switch. Users also can enable/disable the DHCP
Relay on a specific VLAN. If the DHCP Relay on the Switch is disabled, the DHCP Relay is
disabled on all VLANs even some of the VLAN DHCP Relay are enabled.
Applications
Application-1 (Over a Router)
The DHCP cleint-1 and DHCP client-2 are located in different IP segments. But they
allocate IP address from the same DHCP server.
DHCP Client-1 Switch Router Switch DHCP Client-2
DHCP Server
Application-2 (Local in different VLANs)
The DHCP cleint-1 and DHCP client-2 are located in different VLAN. But they allocate IP
address from the same DHCP server.
Switch DHCP Relay agent
Server client client client client client client client
VLAN 1: port 1, 2 (Management VLAN)
VLAN 2: port 3, 4
1
2
3
4
6
5
7
8
