Zyxel VES-1624FT-55A [174/312] Private format

Chapter 29 DHCP Relay

VES-1624FT-55A User’s Guide

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The slot ID, port number, VPI, VCI and MAC are separated from each other by a forward

slash (/) colon (:) or period (.). An example is “SYSNAME atm 0/10:0.33”.

TR-101 uses the same remote ID sub-option format as the Private format.

29.2.2 Private Format

The DHCP relay agent information feature adds an Agent Information field to the option 82

field of the DHCP headers of DHCP request frames that the IP DSLAM relays to a DHCP

server. The Agent Information field that the IP DSLAM adds contains an “Agent Circuit-ID

sub-option” that includes the port number, VLAN ID and optional information about the port

where the DHCP request was received.

The following figure shows the format of the Agent Circuit ID sub-option. The 1 in the first

field identifies this as an Agent Circuit ID sub-option. The length N gives the total number of

octets in the Agent Information Field. If the configuration request was received on an xDSL

port, a 6-byte IP DSLAM's MAC address is added. The last field (A) can range from 0 to 24

bytes and is optional information (that you specify) about this relay agent.

Figure 91 DHCP Relay Agent Circuit ID Sub-option Format

The Agent Information field that the IP DSLAM adds also contains an “Agent Remote-ID

sub-option” of information that you specify.

The following figure shows the format of the Agent Remote ID sub-option. The 2 in the first

field identifies this as an Agent Remote ID sub-option. The length N gives the total number of

octets in the Agent Information Field. Then there is the number of the port (in plain text

format) upon which the DHCP client request was received. The next field (B in the figure) is 0

to 23 bytes of optional information that you specify. This is followed by the name and

telephone number configured for the xDSL port. The port number, optional information (B in

the figure), xDSL name and xDSL telephone number fields are separated by forward slashes.

Figure 92 DHCP Relay Agent Remote ID Sub-option Format

29.3 DHCP Relay Screen

To open this screen, click Advanced Application > DHCP Relay.

Table 55 DHCP Relay Agent Circuit ID Sub-option Format: TR-101 for VDSL

1Nhostname / A / IP “ eth “ Slot ID / Port No.

Table 56 DHCP Relay Agent Circuit ID Sub-option Format: TR-101 for ADSL

1Nhostname / A / IP “ atm “ Slot ID / Port No. : VPI . VCI

MAC Address (6-byte)