Concept Guide

Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
8.3.16.1 Introduced on the MXL 10/40GbE Switch IO Module.
Usage Information
You can add multiple DHCP servers by entering the ip helper-address command multiple times. If multiple
servers are dened, an incoming request is sent simultaneously to all congured servers and the reply is forwarded
to the DHCP client.
The Dell Networking OS uses standard DHCP ports, that is UDP ports 67 (server) and 68 (client) for DHCP relay
services. It listens on port 67 and if it receives a broadcast, the software converts it to unicast, and forwards to it
to the DHCP-server with source port=68 and destination port=67.
The server replies with source port=67, destination port=67 and the system forwards to the client with source
port=67, destination port=68.
ip helper-address hop-count disable
Disable the hop-count increment for the DHCP relay agent.
Syntax
ip helper-address hop-count disable
To re-enable the hop-count increment, use the no ip helper-address hop-count disable command.
Defaults Enabled; the hops eld in the DHCP message header is incremented by default.
Command Modes CONFIGURATION
Supported Modes Full–Switch
Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
8.3.16.1 Introduced on the MXL 10/40GbE Switch IO Module.
Usage Information This command disables the incrementing of the hops eld when boot requests are relayed to a DHCP server
through the Dell Networking OS. If the incoming boot request already has a non-zero hops eld, the message is
relayed with the same value for hops. However, the message is discarded if the hops eld exceeds 16, to comply
with the relay agent behavior specied in RFC 1542.
Related Commands
ip helper-address — species the destination broadcast or host address for DHCP server requests.
show running-cong — displays the current conguration and changes from the default values.
ip host
Assign a name and IP address to be used by the host-to-IP address mapping table.
Syntax
ip host name ip-address
To remove an IP host, use the no ip host name [ip-address] command.
618 IPv4 Routing