Step 4—Interpret the MAC Log File and Take Action
14 Cisco IOS Release 12.0(5)T
Event 1—Wait for the Link to Come Up
When the Cisco uBR924 cable access router is powered on and begins initialization, the first event
that occurs is that the MAC layer informs the cable access router drivers that it needs to reset. The
LINK_DOWN and LINK_UP fields are similar to the shut and no shut conditions on a standard Cisco
interface.
uBR924# show controllers cable-modem 0 mac log
528302.040 CMAC_LOG_LINK_DOWN
528302.042 CMAC_LOG_RESET_FROM_DRIVER
528302.044 CMAC_LOG_STATE_CHANGE wait_for_link_up_state
528302.046 CMAC_LOG_DRIVER_INIT_IDB_SHUTDOWN 0x08098D02
528302.048 CMAC_LOG_LINK_DOWN
528308.428 CMAC_LOG_DRIVER_INIT_IDB_RESET 0x08098E5E
528308.432 CMAC_LOG_LINK_DOWN
528308.434 CMAC_LOG_LINK_UP
Event 2—Scan for a Downstream Channel, then Synchronize
Different geographical regions and different cable plants use different frequency bands. The
Cisco uBR924 cable access router uses a built-in default frequency scanning feature to address this
issue. After the Cisco uBR924 finds a successful downstream frequency channel, it saves the channel
to NVRAM. The Cisco uBR924 recalls this value the next time it needs to synchronize its frequency.
The CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND field tells you what frequency the Cisco
uBR924 will scan for. The CMAC_LOG_WILL_SEARCH_SAVED_DS_FREQUENCY field tells you the
frequency the Cisco uBR924 locked onto and saved to NVRAM for future recall. The
CMAC_LOG_DS_64QAM_LOCK_ACQUIRED field communicates the same information. The
CMAC_LOG_DS_CHANNEL_SCAN_COMPLETED field indicates that the scanning and synchronization was
successful.
508144.348 CMAC_LOG_STATE_CHANGE ds_channel_scanning_state
508144.350 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 88/453000000/855000000/6000000
508144.354 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 89/93000000/105000000/6000000
508144.356 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 90/111250000/117250000/6000000
508144.360 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 91/231012500/327012500/6000000
508144.362 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 92/333015000/333015000/6000000
508144.366 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 93/339012500/399012500/6000000
508144.370 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 94/405000000/447000000/6000000
508144.372 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 95/123015000/129015000/6000000
508144.376 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 96/135012500/135012500/6000000
508144.380 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 97/141000000/171000000/6000000
508144.382 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 98/219000000/225000000/6000000
508144.386 CMAC_LOG_WILL_SEARCH_DS_FREQUENCY_BAND 99/177000000/213000000/6000000
508144.390 CMAC_LOG_WILL_SEARCH_SAVED_DS_FREQUENCY 699000000
508145.540 CMAC_LOG_UCD_MSG_RCVD 3
508146.120 CMAC_LOG_DS_64QAM_LOCK_ACQUIRED 699000000
508146.122 CMAC_LOG_DS_CHANNEL_SCAN_COMPLETED
A frequency band is a group of adjacent channels. These bands are numbered from 88 to 99. Each
band has starting and ending digital carrier frequencies and a 6 MHz step size. For example, a search
of EIA channels 95-97 is specified using band 89. The starting frequency is 93 MHz, the ending
frequency is 105 MHz.
The Cisco uBR924’s default frequency bands correspond to the North American EIA CATV channel
plan for 6 MHz channel slots between 90 MHz and 858 MHz. For example, EIA channel 95 occupies
the slot 90-96 MHz. The digital carrier frequency is specified as the center frequency of 93 MHz.
Channel 95 is usually specified using the analog video carrier frequency of 91.25 MHz, which lies
1.75 MHz below the center of the slot.