Cisco Broadband Cable Command Reference Guide

Chapter 2 Cisco Cable Modem Termination System Commands
cable source-verify
Syntax Description
Defaults Disabled
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Cisco Broadband Cable Command Reference Guide
cable source-verify
To enable verification of IP addresses for CMs and CPE devices on the upstream, use the cable
source-verify command in cable interface or subinterface configuration mode. To disable verification,
use the no form of this command.
cable source-verify [dhcp | leasetimer value]
no cable source-verify
Command Modes Cable interface and subinterface configuration
Command History
dhcp (Optional) Specifies that queries will be sent to verify unknown source
IP addresses in upstream data packets.
leasetimer value (Optional) Specifies the time, in minutes, for how often the router
should check its internal CPE database for IP addresses whose lease
times have expired. The valid range for value is 1 to 240 minutes, with
no default.
Note The leasetimer option takes effect only when the dhcp option
is also used on an interface. Also, this option is supported only
on the master interface and cannot be configured on
subinterfaces. Configuring it for a master interface
automatically applies it to all subinterfaces.
Note Configuring the cable source-verify command on the master interface of a bundle will
configure it for all of the slave interfaces in the bundle as well.
Release Modification
11.3 XA This command was introduced.
12.0(7)T The dhcp keyword was added.
12.0(10)SC, 12.1(2)EC Support was added for these trains.
12.1(3a)EC Subinterface support was added.
12.1(13)EC,
12.2(11)BC1
The leasetimer keyword was added.
Usage Guidelines The cable source-verify command helps to prevent the spoofing of IP addresses by CMs or their CPE
devices by verifying that the upstream packets coming from each CM are known to be associated with
the IP address in that packet. Packets with IP addresses that do not match those associated with the CM
are dropped.
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