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Chapter 6
Cable CPE Commands
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The ping docsis command is a DOCSIS-compliant process that can be used with any two-way
Note
DOCSIS-compliant CM; the CM does not require any special features or code. The ping docsis
command cannot be used with telco-return CMs.
Table 6-2
Table 6-2
Output Character Description
!
.
a
f
If a CM is already in the flap list, the ping docsis command increments the hit, miss, and
Note
power-adjustment fields for it in the cable flap list.
Examples
The following example shows a default ping docsis command that sends five packets to the CM with the
MAC address of 0010.7bb3.fd19, with a response being received for each:
Router# ping docsis 0010.7bb3.fd19
OL-1581-07
The CM is still in the registration process and has not yet come completely online. In particular, the
CM could be waiting for the DHCP server to assign it an IP address.
Severe interference or other faults on the physical layer (either the upstream or downstream).
Significant upstream signal error, distortion, or amplitude errors, often resulting in frequent power
adjustments (which are shown in the cable flap list).
A non-DOCSIS compliant upstream carrier-to-noise power ratio (C/N) that is between 14 and
21 dB, along with a mixed modulation profile, such as ranging request/response messages being sent
in QPSK mode and short and long data grants in 16-QAM mode.
explains the different characters that can appear in the output for the ping docsis command:
ping docsis Command Output Characters
Indicates that a successful response was received from the ping request. This
indicates that the CM is reachable from the CMTS and can respond to CMTS
requests at the DOCSIS MAC layer.
Indicates that a DOCSIS ping request was sent out but that the ping request timed
out without receiving a response. This indicates that the CM is having difficulties
maintaining DOCSIS MAC layer connectivity to the CMTS.
Note
If the ping docsis command displays a number of periods (.) along with
exclamation points (!), it strongly indicates the presence of RF noise or
physical cable and plant issues that is causing a loss of MAC layer
connectivity.
Indicates that a response was received but that an adjustment of frequency, power, or
timing was also made in the response. This indicates that, although the upstream
channel is functional, some sort of problem is forcing power averaging and other
misreads of the upstream received power signals.
Indicates that the DOCSIS ping request failed because the CM is offline, and
therefore MAC-layer communication is not possible. This indicates that the CM had
previously registered with the CMTS, but that at some point it stopped responding
to the DOCSIS station maintenance messages and that the CMTS eventually marked
the CM as offline. The CM might have lost power or might have been disconnected
from the coaxial cable.
Cisco Broadband Cable Command Reference Guide
ping docsis
6-63
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