Edge-Core ES4626 User Manual page 362

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
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
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
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
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):
Switch3(Config)#service dhcp
Switch3(Config)#ip dhcp relay information option
Switch3(Config)#ip forward-protocol udp bootps
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 helper 192.168.10.88
Linux ISC DHCP Server supports option 82, its configuration file /etc/dhcpd.con is
ddns-update-style interim;
ignore client-updates;
class "Switch3Vlan2Class1" {
match if option
agent.remote-id=00:03:0f:02:33:01;
}
class "Switch3Vlan2Class2" {
match if option
agent.remote-id=00:03:0f:02:33:01;
}
subnet 192.168.102.0 netmask 255.255.255.0 {
option routers 192.168.102.2;
option subnet-mask 255.255.255.0;
option domain-name "example.com.cn";
option domain-name-servers 192.168.10.3;
authoritative;
agent.circuit-id =
agent.circuit-id =
362
"Vlan2+Ethernet1/2"
"Vlan2+Ethernet1/3"
and option
and option