TP-Link T1600G-28PS Jetstream Smart Switches User Guide - Page 520

Configuring DHCP Service Configuration Examples Switch#show ip dhcp l2relay information interface gigabitEthernet 1/0/1 Interface Option 82 Status Operation Strategy Format Circuit ID ... Gi1/0/2 Enable Replace Normal Group2 ... 5.5.4 Configuring the DHCP Server Note: •• Make sure the DHCP server supports Option 82 and more than one DHCP address pool. •• To make sure the DHCP server can reach the computers, you can create static routes or enable dynamic routing protocol like RIP on the DHCP server. •• In this section, we use different notations to distinguish ASCII strings from hexadecimal numbers. An ASCII string is enclosed with quotation marks, such as "123", while a hexadecimal number is divided by colon into parts of two digits, such as 31:32:33. On the DHCP server, you need to create two DHCP classes to identify the Option 82 payloads of DHCP request packets from Group 1 and Group 2, respectively. In this example, the DHCP relay agent uses the customized circuit ID and default remote ID in TLV format. According to packet format described in Table 1-1 and Table 1-2, the suboptions of the two groups are as shown in the following table. Table 5-2 Sub-options of Group1 and Group 2 Group Sub-option Type (Hex) Length (Hex) Value Circuit ID 00 06 "Group1" as an ASCII string (or 47:72:6F:75:70:31 in hexadecimal) 1 Remote ID 00 06 00:00:FF:FF:27:12 Circuit ID 00 06 "Group2" as an ASCII string (or 47:72:6F:75:70:32 in hexadecimal) 2 Remote ID 00 06 00:00:FF:FF:27:12 The configuration file /etc/dhcpd.conf of the Linux ISC DHCP Server is: ddns-update-style interim; ignore client-updates; # Create two classes to match the pattern of Option 82 in DHCP request packets from # Group 1 and Group 2, respectively. # The agent circuit ID inserted by the DHCP relay switch is 8 byte long in TLV format, one # byte for Type, one byte for Length, and 6 bytes for Value. Therefore, the offset is 2 and the length is 6. User Guide 495