Troubleshooting guide

5-7
Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 5 Troubleshooting DOCSIS Networks
Understanding Initialization States
Caution Running debug commands on a uBR with more than a handful of modems may cause the uBR to halt the
system in order to keep up with the debugging. In this case, all the modems may lose sync and debugging
will be useless.
If no packets are seen in debug messages, check the configuration of the “ip helper-address” statement
on the cable interface to which this modem is attached. If this is configured correctly and a packet trace
of the DHCP server subnet also reveals no DHCP packets from the modem, then the next place to look
is the output errors of the modem's cable interface, or the input errors of the cable interface of the uBR.
It might be a good idea to boost the transmitter power a bit more with more attenuation.
If you can see that packets are being transmitted onto the DHCP server subnet, it would be a good idea
to double-check the modem debug messages to see if there are parameter request or assignment errors.
This is the stage of troubleshooting where you should investigate the routing between the modem and
the DHCP server. It is also advisable to double-check the DHCP server configuration.
Establish TOD State
MAC State --->>> 'establish_tod_state'
After a modem has acquired its network parameters, it must request the time of day from a Time Of Day
(TOD) server. TOD uses a UTC timestamp (seconds from January 1, 1970) combined with the time offset
option value from DHCP to calculate the current time. The time is used for syslog and event log
timestamps.
Time of day errors almost always point to a DHCP misconfiguration. Possible misconfigurations that can
result in TOD errors are IP address, gateway address misconfigurations, or the wrong TOD server
address. Again, start troubleshooting locally by examining the DHCP parameters the modem has stored,
using the following command:
-> cmShowDhcpParameters
or:
-> cmAddLogValues (“SEV_ALL FAC_DHCP”)
The latter will give debug output of DHCP actions and tasks.
Also check the modem routing table with the vxWorks routeShow command.
Security Association State
MAC State --->>> 'security_association_state'
This is a placeholder for a state yet to be defined. It is envisioned that a security association with a
security server will provide IPsec-like security for the modems. Questions about its design and
implementation are still being discussed. In the meantime, DOCSIS 1.0 requires modems to support a
future definition of this state including the DHCP option for a security server. It is unlikely to find a
modem having a problem with this state until it is defined in DOCSIS and implemented on the modem.