Troubleshooting guide

7-12
Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 7 Troubleshooting the CMTS
Troubleshooting the Cisco uBR7246VXR
1w3d: 871160.686 CMAC_LOG_RNG_REQ_QUEUED 6
1w3d: 871161.690 CMAC_LOG_RNG_REQ_TRANSMITTED
1w3d: 871161.690 CMAC_LOG_RNG_RSP_MSG_RCVD
1w3d: 871161.694 CMAC_LOG_ADJUST_TX_POWER -36
1w3d: 871161.694 CMAC_LOG_RANGING_CONTINUE
1w3d: 871162.698 CMAC_LOG_RNG_REQ_TRANSMITTED
1w3d: 871162.898 CMAC_LOG_T3_TIMER
1w3d: 871163.734 CMAC_LOG_RNG_REQ_TRANSMITTED
1w3d: 871163.934 CMAC_LOG_T3_TIMER
1w3d: 871164.766 CMAC_LOG_RNG_REQ_TRANSMITTED
1w3d: 871164.966 CMAC_LOG_T3_TIMER
131.CABLEMODEM.CISCO: 1w3d: %UBR900-3-RESET_T3_RETRIES_EXHAUSTED: R03.0 Ranging
1w3d: 871164.966 CMAC_LOG_RESET_T3_RETRIES_EXHAUSTED
1w3d: 871164.966 CMAC_LOG_STATE_CHANGE reset_interface_state
1w3d: 871164.966 CMAC_LOG_STATE_CHANGE reset_hardware_state
Note: init(r1) is ranging_1_state and init(r2) is ranging_2_state
You can get an indication of the Transmit power on the MTA by displaying the following command:
#sh cont cable-modem 0
BCM Cable interface 0:
CM unit 0, idb 0x2010AC, ds 0x86213E0, regaddr = 0x800000, reset_mask 0x80
station address 0050.7366.2223 default station address 0050.7366.2223
PLD VERSION: 32
MAC State is wait_for_link_up_state, Prev States = 2
MAC mcfilter 00000000 data mcfilter 00000000
MAC extended header ON
DS: BCM 3116 Receiver: Chip id = 2
US: BCM 3037 Transmitter: Chip id = 30AC
Tuner: status=0x00
Rx: tuner_freq 0, symbol_rate 5055932, local_freq 11520000
snr_estimate 30640, ber_estimate 0, lock_threshold 26000
QAM not in lock, FEC not in lock, qam_mode QAM_64
Tx: tx_freq 27984000, power_level 0x20 (8.0 dBmV), symbol_rate 8 (1280000 sym/s)
If a cable modem cannot proceed out of ranging state, the likely cause is an insufficient transmit power
level. Transmit power can be adjusted by adjusting attenuation at the low frequency port. Increased
attenuation will result in increased transmit power levels. Roughly 20 - 30 dBmV of attenuation is a good
place to start.
After initial ranging init(r1) the cable modem proceeds onto init(r2) which is where the cable modem
must configure the transmit timing offset and power level to ensure that transmissions from the modem
are received at the correct time and are at an acceptable input power level at the Cisco uBR7246VXR
receiver. This is performed through a conversation of unicast RNG-REQ and RNG-RSP messages. The
RNG-RSP messages contain power and timing offset corrections the cable modem must make.
the cable modem continues to transmit RNG-REQ and perform adjustments per RNG-RSP until the
RNG-RSP message indicates ranging success or ranging complete by reaching the init(rc) state. If a
cable modem cannot proceed out of init (r2) the transmit power needs to be refined. Below is an output
display of an MTA in init(r2) state. Note the asterisk (*) symbol next to the Rec Power column indicating
that the noise power adjustment method is active for this modem. If you see an exlamation point (!) this
means the cable modem has reached its maximum transmit power.
#show cable modem
Interface Prim Sid
Online
State
Timing
Offset
Rec
Power QoS CPE IP address MAC address
Cable2/0/U0 5 init(r2) 2289 *4.00 2 0 10.1.1.25 0050.7366.2223