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Configuring Subscriber-End Broadband Access Router Features
Subscriber-End Broadband Access Router Basic Troubleshooting
MC-635
Cisco IOS Multiservice Applications Configuration Guide
In the following paragraphs, a sample log file is broken down into the chronological sequence of events
listed below. Sample comments are also included in the log file.
• Event 1—Wait for the Link to Come Up
• Event 2—Scan for a Downstream Channel, then Synchronize
• Event 3—Obtain Upstream Parameters
• Event 4—Start Ranging for Power Adjustments
• Event 5—Establish IP Connectivity
• Event 6—Establish the Time of Day
• Event 7—Establish Security
• Event 8—Transfer Operational Parameters
• Event 9—Perform Registration
• Event 10—Comply with Baseline Privacy
• Event 11—Enter the Maintenance State
Event 1—Wait for the Link to Come Up
When the Cisco uBR900 series cable access router is powered up and begins initialization, the MAC
layer first 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 RF frequency bands. A frequency
band is a group of adjacent 6 MHz-wide 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 to 97 is specified using band 89. The starting frequency of band 89 is 93 MHz; the ending
frequency is 105 MHz.
The Cisco uBR900 series’ default frequency bands correspond to the North American EIA CATV
channel plan for 6 MHz channel slots from 90 to 858 MHz. For example, EIA channel 95 occupies the
90-to-96 MHz slot. The digital carrier frequency is specified as the center frequency of the slot, which
is 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.
Some CATV systems use alternative frequency plans such as the Incrementally Related Carrier (IRC)
plan and Harmonically Related Carrier (HRC) plan. Cisco uBR900 series cable access routers support
both of these plans. Most of the IRC channel slots overlap the EIA plan.
The Cisco uBR900 series uses a built-in default frequency scanning feature to find and lock onto a
downstream channel. After the cable access router successfully finds a downstream frequency channel,
it saves the channel to NVRAM. The router recalls this value the next time it needs to synchronize its
frequency.