User's Manual

31-7
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.circuit-id = "Vlan2+Ethernet1/0/2" and option agent.remote-id=00:03:4f:02:33:01;
}
class "Switch3Vlan2Class2" {
match if option agent.circuit-id = "Vlan2+Ethernet1/0/3" and option agent.remote-id=00:03:4f: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;
pool {
range 192.168.102.21 192.168.102.50;
default-lease-time 86400; #24 Hours
max-lease-time 172800; #48 Hours
allow members of "Switch3Vlan2Class1";
}
pool {
range 192.168.102.51 192.168.102.80;
default-lease-time 43200; #12 Hours
max-lease-time 86400; #24 Hours
allow members of "Switch3Vlan2Class2";
}
}
Now, the DHCP server will allocate addresses for the network nodes from Switch1 which are relayed by
Switch3 within the range of 192.168.102.21 ~ 192.168.102.50, and allocate addresses for the network nodes
from Switch1 within the range of 192.168.102.51～192.168.102.80.
31.4 DHCP option 82 Troubleshooting
 DHCP option 82 is implemented as a sub-function module of DHCP Relay Agent. Before using it, users
should make sure that the DHCP Relay Agent is configured correctly.
 DHCP option 82 needs the DHCP Relay Agent and the DHCP server cooperate to finish the task of
allocating IP addresses. The DHCP server should set allocating policy correctly depending on the
network topology of the DHCP Relay Agent, or, even the Relay Agent can operate normally, the
allocation of addresses will fail. When there is more than one kind of Relay Agent, please pay attention
to the retransmitting policy of the interface DHCP request messages.