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Option 82 contains two common sub-options: Circuit ID and Remote ID. Circuit ID is mainly used to identify the VLAN and the interface of the client, Remote ID identifies the device from which the client accessed, usually the MAC address of the device.
Packet Format
Circuit ID Sub-option
Circuit ID includes three types: Type 0 (value is port index), Type 1 (value is port name + VLAN ID) and Type 2 (value is port description + VLAN ID). The format is listed below by types.
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DHCP snooping Option 82 can be enabled on Switch 1, and DHCP relay Option 82 can be enabled on Switch 2. It is optional. But if Option 82 is inserted on Switch 1, DHCP relay Option 82 trust all should be enabled on Switch 2.
Option 12 and Option 42
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DHCP options are additional parameters that can be passed from a DHCP server to DHCP clients during the IP address assignment process. These options provide additional configuration information beyond just the IP address and subnet mask. In addition to supporting Option 82, PICOS also supports Option 12 and Option 42.
Option 12: This option is used to specify the hostname of the DHCP client. When a DHCP client requests an IP address from a DHCP server, it can include its hostname in the DHCP request message using Option 12. The DHCP server can then use this information to assign a hostname to the client along with its IP address lease.
Option 42: This option is used to specify the Network Time Protocol (NTP) servers available to the DHCP client. NTP servers are used by network devices to synchronize their clocks with a central time source. Option 42 allows the DHCP server to provide the IP addresses of one or more NTP servers to DHCP clients during the address assignment process. This ensures that clients can synchronize their clocks accurately, which is important for network operations and logging purposes.
Interaction with Other Protocols
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