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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
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
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
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 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 relayed with the same value for hops. However, the message is discarded if the hops field
exceeds 16, to comply with the relay agent behavior specified in RFC 1542.
Related
Commands
ip helper-address — specifies the destination broadcast or host address for DHCP server requests.
show running-config — displays the current configuration and changes from the default values.
550 IPv4 Routing