Access Control List Screens; Dhcp Relay Overview; Dhcp Relay Agent Information Option (Option 82); Private Format - ZyXEL Communications MSC1024G Series User Manual

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Access Control List Screens

This chapter describes the ACL (Access Control List) screens.

5.1 DHCP Relay Overview

DHCP (Dynamic Host Configuration Protocol, RFC 2131 and RFC 2132) allows individual
clients to obtain TCP/IP configuration at start-up from a DHCP server. You can configure the
system to relay client TCP/IP configuration requests to a DHCP server and the server's
responses back to the clients.
You can configure the system to forward client DHCP requests from different VLANs to
specific DHCP servers.

5.1.1 DHCP Relay Agent Information Option (Option 82)

The system can add information to DHCP requests that it relays to a DHCP server. This helps
provide authentication about the source of the requests. You can also specify additional
information for the system to add to the DHCP requests that it relays to the DHCP server.
Please refer to RFC 3046 for more details.
The DHCP relay agent information feature adds an Agent Information field to the option 82
field of the DHCP headers of client TCP/IP configuration request frames that the management
switch card relays to a DHCP server. The MSC supports two formats for the DHCP relay agent
information: Private and TR-101.

5.1.2 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 MSC relays to a DHCP server.
The Agent Information field that the MSC adds contains an "Agent Circuit-ID sub-option"
that includes the slot and port numbers, VLAN ID and optional information about the slot and
port on which the DHCP request was received.
The following table shows the format of the private Agent Circuit ID sub-option. The (binary)
"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 a DSL port, a 1-byte Slot No field specifies the ingress slot number, and a 1-byte
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