Specifications

Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval 100 ms
TX Backoff Start 0, TX Backoff End 4
Modulation Profile Group 1
Concatenation is enabled
part_id=0x3137, rev_id=0x03, rev2_id=0xFF
nb_agc_thr=0x0000, NB_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 128
Bandwidth Requests = 0x335
Piggyback Requests = 0xA
Invalid BW Requests= 0x0
Minislots Requested= 0xA52
Minislots Granted = 0xA52
Minislot Size in Bytes = 32
Map Advance (Dynamic) : 2447 usecs
UCD Count = 46476
DES Ctrl Reg#0 = C000C043, Reg#1 = 0
VXR#
Make sure that the physical CMTS cable connections are not loose or disconnected and that the cable modem
card is firmly seated in its chassis slot with the installation screws tight. Also that you have entered the correct
slot and port numbers for the upstream interface you are checking.
Remember that the upstream channel on the Cisco cable modem is by default shut down and you will need to
issue the no shut command to activate it.
Note: The upstream frequency displayed in the show controllers cable command output might not match the
frequency that you entered when you set the upstream frequency. The Cisco CMTS might select an upstream
frequency close to the frequency you entered that offers better performance. The minimum upstream
frequency step size on the MC16C is 32 kHz. The Cisco CMTS selects the closest frequency available. See
the explanation of the cable upstream 0 frequency command for this.
Note: Some cable systems cannot reliably transport frequencies near the allowed band edges. The wider the
upstream channel (in MHz), the more difficulty you might have. Enter a center frequency between 20 and 38
MHz if you experience problems. The Cisco CMTS will then command the cable modems to use a
downstream frequency within this range. Setting the right upstream frequency is the most important task in
designing the RF network. The upstream operates on the range 5 to 42 MHz. Below 20MHz it is common to
find a lot of interference. Contrary to a lab environment, setting up the upstream in a live network represents
the biggest RF challenge.
Note: Higher symbol rates are more susceptible to RF noise and interference. If you use a symbol rate or
modulation format beyond the capabilities of your HFC network you might experience packet loss or poor
cable modem connectivity. This can be seen in the figure below where a higher CNR is needed to maintain the
same bit error rate (BER) with more complex modulation formats.
Cisco − Determining RF or Configuration Issues On the CMTS