Service Manual

ip helper-address
Specify the address of a DHCP server so that DHCP broadcast messages can be forwarded when the DHCP server is not on the same
subnet as the client.
Syntax
ip helper-address ip-address
To remove a DHCP server address, use the no ip helper-address command.
Parameters
ip-address Enter an IP address in dotted decimal format (A.B.C.D).
Defaults Not configured.
Command Modes INTERFACE
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 defined, an incoming request is sent simultaneously to all configured 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 field in the DHCP message header is incremented by default.
Command Modes CONFIGURATION
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 field 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 field, the message is
574 IPv4 Routing