Troubleshooting guide

7-7
Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 7 Troubleshooting the CMTS
Troubleshooting the Cisco uBR7246VXR
Note At the MTA side a good command to use is show controllers cable-modem 0 mac state and look at
the MAC State field.
The following sections discuss each State value, what the possible causes are, and what steps can be
taken to arrive at the correct state (online).
Offline State
In some cases the cable modem may cycle through other states then back to offline. The following list
gives the most common reasons for a cable modem not to achieve QAM lock:
• Weak carrier signal (too much noise)
• Incorrect downstream center frequency
• Incorrect frequency specified in the DOCSIS file
• Absence of downstream digital QAM modulated signal
• Incorrect frequency specified in cable modem change-frequency on the Cisco uBR7246VXR
The following is a portion of the output from show controllers cable-modem 0 entered at the router end:
#sh cont c 0
BCM Cable interface 0:
CM unit 0, idb 0x8086C88C, ds 0x8086E460, regaddr = 0x2700000, reset_mask 0x80
station address 0030.96f9.65d9 default station address 0030.96f9.65d9
PLD VERSION: 1
Concatenation: ON Max bytes Q0: 2000 Q1: 2000 Q2: 2000 Q3: 2000
MAC State is ds_channel_scanning_state, Prev States = 3
MAC mcfilter 01E02F00 data mcfilter 00000000
MAC extended header ON
DS: BCM 3300 Receiver: Chip id = BCM3300
US: BCM 3300 Transmitter: Chip id = 3300
init (t) TOD exchange started
init(o) Option file transfer started
online Cable modem registered, enabled for data
online(d) Cable modem registered, but network access for the cable modem is disabled
online(pk) Cable modem registered, BPI enabled and KEK assigned
online(pt) Cable modem registered, BPI enabled and TEK assigned
reject (pk) KEK modem key assignment rejected
reject (pt) TEK modem key assignment rejected
reject (m) Cable modem did attempt to register; registration was refused due to bad MIC
(Message Integrity Check)
reject (c) Cable modem did attempt to register; registration was refused due to bad COS
(Class of Service)
Table 7-1 State Values (continued)
State Value Description