Chapter 17: IP Packet Filters, Subscriber Management
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
579
The Debug IP Packet Capture utility has been designed to be non-interfering. Though it is possible to configure IP filters
that capture huge numbers of packets, the hardware and software that gather the packets only allow as many through as
can currently be processed. System performance and throughput will not suffer even if IP filters capture too many packets.
If a filter matches so many packets that the hardware and software cannot process them, then these packets will be
dropped from the log. The log keeps a counter that shows how many packets were dropped from the log. This does not
mean that the packets were prevented from reaching their destinations; it simply means that these packet captures were
not included in the log.
Filter Logging in the C4/c CMTS
This function configures the data packet logging operation that the CMTS performs when a match occurs on a packet.
Use the following command to enable/disable a specific IP filter to capture packets and send them to the capture buffer:
configure [no] cable filter group <
group> index <index> log [parameter name <value>]
To disable packet capture on all filters, use the following command:
configure no cable filter log
This example drops packets with an IP: 10.119.30.255 with mask 255.255.255.0, but also logs data to the CMTS output:
configure cable filter group 10 index 1 log src-ip 10.119.30.255 src-mask 255.255.255.0 match-
action drop
The logging of captured packets to the CMTS output is turned on/off with the following commands:
configure [no] logging debug ip packet brief [slot <
slot>]
The command above uses the brief option. It logs the interface on which the packet was received, including the direction,
if appropriate. It also logs the source of the capture, i.e., IP filter group/index, as well as the SIP, DIP, and protocol.
The second version of the command, which corresponds to the detail option, logs the contents of the packet, limited to the
length that the hardware supports in the capture buffer.
configure [no] logging debug ip packet detail [slot <
slot>]
If neither brief nor detail log option is enabled, the captured packets information is still collected but discarded. The
captured buffer data is sent to the logging or syslog output of the CMTS.
To display the captured packets:
show logging history