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Table Of Contents
Cable Modem and Host Subnet Addressing
Cable Modem and Host Subnet Addressing
Feature Overview
This feature enables a Cisco Universal Broadband Router (uBR) to manipulate the giaddr field in client Dynamic Host Control Protocol (DHCP) requests forwarded to DHCP servers in a Data Over Cable Service Interface Specifications (DOCSIS) environment.
Benefits
This feature provides hints to the DHCP server as to where (that is, on which IP subnet) the server should allocate addresses to the requesting client.
Supported Platform
Cisco uBR7200 Series Cable Router
Supported MIBs and RFCs
MIBs
None
RFCs
None
Configuration Tasks
None
Command Reference
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
cable dhcp-giaddr
To control giaddr, use the cable dhcp-giaddr Interface Configuration command. Use the no form of this command to set dhcp-giaddr control to the default.
cable dhcp-giaddr [policy | primary]
no cable dhcp-giaddrSyntax Description
policy
Selects the control policy, so the primary address is used for cable modems and the secondary addresses are used for hosts.
primary
Always selects the primary address to be used for giaddr.
Defaults
No control of giaddr from the cable code.
Command Modes
Interface Configuration
Command History
Usage Guidelines
This command allows you to configure the cable modem subnet as the primary address and the host subnet as the secondary address.
Examples
The following example sets the primary address to be used always for giaddr.
Router(config-if)#cable dhcp-giaddr primary
