Cisco Cisco IOS Software Release 12.1(3)EC

Turning the scrambler off can cause packet loss, and is only 
used in lab testing environments.

Errors or incompatible configurations in the burst profile(s) 
cause modems to either drop connectivity, drop short or long 
data packets, or fail to connect to the network. It is possible to 
build a burst profile set for which no implementation of a 
DOCSIS receiver is capable of receiving the modem’s 
transmission.

160 Ksymbol/sec and 2560 Ksymbol/sec data rates are highly 
sensitive to unique word length, preamble length, and FEC 
sizing. Incorrect choices for these values can cause poor or no 
connectivity at these symbol rates.

seed = Scrambler seed in hexidecimal format. Valid values are 
from 0x0000 to 0x7FFF.

diff = Enable or disable differential encoding. Valid entries are 
diff and no-diff.

pre-len = Preamble length in bits. Valid values are from 2 to 
128.

last-cw = Handling of FEC for last code word. Valid entries are 
fixed for fixed code word length and shortened for shortened 
last code word.

uw-len = Upstream unique word length. Enter uw8 for 8-bit 
unique words or uw16 for 16-bit unique code words.

Router(config)# interface

Configures the interface where:

 = cable

slot 

= slot number in chassis (slot numbers begin with a 0)

 = port number on cable modem slot (port numbers begin 

with a 0)

Router(config-int)# cable upstream 

port-number modulation-profile 

Adds the modulation profile to the interface.

port number on cable modem slot (port numbers 

begin with a 0)

= The primary modulation profile 

added to the interface.

secondary-profile-number 

= The additional modulation 

profile added to the interface.

Router(config-int)# exit

Enter exit to go back to the configuration mode.