Managing The Dhcp Relay Agent - Siemens RX1500 User Manual

RUGGEDCOM ROX II
User Guide
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Figure 323: Cellular Network Configuration Table
1. Add Button
3. Click Delete next to the chosen profile.
4. Click Commit to save the changes or click Revert All to abort. A confirmation dialog box appears. Click OK
to proceed.
5. Click Exit Transaction or continue making changes.
Section 5.14

Managing the DHCP Relay Agent

A DHCP Relay Agent is a device that forwards DHCP packets between clients and servers when they are not on
the same physical LAN segment or IP subnet. The feature is enabled if the DHCP server IP address and a set of
access ports are configured.
DHCP Option 82 provides a mechanism for assigning an IP Address based on the location of the client device in
the network. Information about the client's location can be sent along with the DHCP request to the server. Based
on this information, the DHCP server makes a decision about an IP Address to be assigned.
DHCP Relay Agent takes the broadcast DHCP requests from clients received on the configured access port and
inserts the relay agent information option (Option 82) into the packet. Option 82 contains the VLAN ID (2 bytes)
and the port number of the access port (2 bytes: the circuit ID sub-option) and the switch's MAC address (the
remote ID sub-option). This information uniquely defines the access port's position in the network. For example,
in ROX II, the Circuit ID for VLAN 2 on Line Module (LM) 4 Port 15 is 00:00:00:02:04:0F.
The DHCP Server supporting DHCP Option 82 sends a unicast reply and echoes Option 82. The DHCP Relay
Agent removes the Option 82 field and broadcasts the packet to the port from which the original request was
received.
The DHCP Relay Agent communicates to the server on a management interface. The agent's IP address is the
address configured for the management interface.
ROX II can be configured to act as a DHCP Relay Agent that forwards DHCP and BOOTP requests from
clients on one layer 2 network to one or more configured DHCP servers on other networks. This allows the
implementation of some measure of isolation between DHCP clients and servers.
The DHCP Relay Agent is configured to listen for DHCP and BOOTP requests on particular Ethernet and VLAN
network interfaces, and to relay to a list of one or more DHCP servers. When a request is received from a client,
ROX II forwards the request to each of the configured DHCP servers. When a reply is received from a server,
ROX II forwards the reply back to the originating client.
Managing the DHCP Relay Agent
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2. Edit Button 3. Delete Button
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Chapter 5
Setup and Configuration
307