Dhcp Option 82 Application Examples - Edge-Core ES4624-SFP Basic Management Manual

16.3 DHCP option 82 Application Examples

DHCP option 82 Application Examples
DHCP Client PC1
DHCP Client PC2
Fig 16-2 a DHCP option 82 typical application example Fig 16-2 a DHCP option 82 typical application example
In the above example, layer 2 switches Switch1 and Switch2 are both connected to In the above example, layer 2 switches Switch1 and Switch2 are both connected to
layer 3 switch Switch3, Switch 3 will transmit the request message from DHCP client to layer 3 switch Switch3, Switch 3 will transmit the request message from DHCP client to
DHCP serer as DHCP Relay Agent. It will also transmit the reply message from the DHCP serer as DHCP Relay Agent. It will also transmit the reply message from the
server to DHCP client to finish the DHCP protocol procedure. If the DHCP option 82 is server to DHCP client to finish the DHCP protocol procedure. If the DHCP option 82 is
disabled, DHCP server cannot distinguish that whether the DHCP client is from the disabled, DHCP server cannot distinguish that whether the DHCP client is from the
network connected to Switch1 or Switch2. So, all the PC terminals connected to Switch1 network connected to Switch1 or Switch2. So, all the PC terminals connected to Switch1
and Switch2 will get addresses from the public address pool of the DHCP server. After and Switch2 will get addresses from the public address pool of the DHCP server. After
the DHCP option 82 function is enabled, since the Switch3 appends the port information the DHCP option 82 function is enabled, since the Switch3 appends the port information
of accessing Switch3 to the request message from the client, the server can tell that of accessing Switch3 to the request message from the client, the server can tell that
whether the client is from the network of Swich1 or Swich2, and thus can allocate whether the client is from the network of Swich1 or Swich2, and thus can allocate
separate address spaces for the two networks, to simplify the management of networks. separate address spaces for the two networks, to simplify the management of networks.
The following is the configuration of Switch3(MAC address is 00:03:0f:02:33:01): The following is the configuration of Switch3(MAC address is 00:03:0f:02:33:01):
Switch3(Config)#service dhcp Switch3(Config)#service dhcp
Switch3(Config)#ip dhcp relay information option Switch3(Config)#ip dhcp relay information option
Switch3(Config)#ip forward-protocol udp bootps Switch3(Config)#ip forward-protocol udp bootps
Switch3(Config)#interface vlan 3 Switch3(Config)#interface vlan 3
Switch3(Config-if-vlan3)#ip address 192.168.10.222 255.255.255.0 Switch3(Config-if-vlan3)#ip address 192.168.10.222 255.255.255.0
Switch3(Config-if-vlan2)#ip address 192.168.102.2 255.255.255.0 Switch3(Config-if-vlan2)#ip address 192.168.102.2 255.255.255.0
Switch3(Config-if-vlan2)#ip helper 192.168.10.88 Switch3(Config-if-vlan2)#ip helper 192.168.10.88
Linux ISC DHCP Server supports option 82, its configuration file /etc/dhcpd.con is Linux ISC DHCP Server supports option 82, its configuration file /etc/dhcpd.con is
ddns-update-style interim; ddns-update-style interim;
Switch1
Vlan2:eth1/3
Switch2
472
DHCP Relay Agent
Switch3
Vlan3
Vlan2:eth1/2
DHCP Server