PLANET WGSW-50040 - Manual (Page 153)

20-10
In the above example, layer 2 Switch1 will transmit the request message from DHCP client to DHCP serer
through enable DHCP Snooping. It will also transmit the reply message from the server to DHCP client to
finish the DHCP protocol procedure. After the DHCP SNOOPING option 82 function is enabled, the Switch1
appends the port information of accessing Switch1 to the request message from the client by option 82.
The following is the configuration of Switch1(MAC address is 00-30-4f-02-33-01):
Switch1(config)#ip dhcp snooping enable
Switch1(config)#ip dhcp snooping binding enable
Switch1(config)# ip dhcp snooping information enable
Switch1(Config-If-Ethernet1/12)#ip dhcp snooping trust
Linux ISC DHCP Server supports option 82, its configuration file /etc/dhcpd.conf is ddns-update-style interim;
ignore client-updates;
class "Switch1Vlan1Class1" {
match if option agent.circuit-id = "Vlan1+Ethernet1/3" and 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;
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 "Switch1Vlan1Class1";
}
}
Now, the DHCP server will allocate addresses for the network nodes from Switch1 within the range of
192.168.102.51 ~ 192.168.102.80.
20.4 DHCP Snooping option 82 Troubleshooting
 To implement the option 82 function of DHCP SNOOPING, the “debug ip dhcp snooping packet”
command can be used during the operating procedure, including adding the option 82 information of
the request message, the option 82 information peeled by the reply message.