uBR7246 (NPE200) shown ! in Rec Power column

[javierf]

Hello,

In show cable modem a lot of CM marked with "!". This sign "indicates that the CM has reached its maximum power transmit level and cannot increase its power level further.", but can i do something for try solve it in uBR?

Thanks

Javier.

[makchitale]

DOCSIS cable modems can adjust their upstream transmission power levels to adjust unstable cable plant signal levels, up to a max allowable power level. Repeated adjustment usually indicates a problem with an amplifier in the upstream return path.

1)Ensure the RF plant is stable (since you mentioned that there are a lot of CMs with “!”)

2)The HFC plant should be designed so that in normal DOCSIS 1.x operation, modems transmit between 42 and 52 dBmV. This gives enough headroom for customer-induced losses, modulation changes, temperature-related issues, and age factors. Designing a lower bound of 42 dBmV helps alleviate noise induced from low-value taps (4, 8, 11 dB).

3) Removing the extra attenuation - RF issue

4) Try the upstream power-adjust

ubr10k-1(config-if)#cable upstream 0 power-adjust ?

continue Minimum power adjustment which set CONTINUE ranging status

noise % of power adjust pkts required for changing the adjustment method

threshold Power adjustment threshold

3) Decrease required receive level power (cable up power-level )

Thanks, Mak

[ysj107]

As a engineer, I have solved this problem in two approach.

1) Please check your Upchannel Impulse noise not S/N, if there are several time period such as morning or evening, plase check noise source and remove it.

2) I tried to handle above methods, but for me it seems minor beneficial to adjust power level at CMTS side. Some other modem will work same problem at another days. Moreover, if you use and control a lots of CMTS with other operator,it is very hard to control which cell is adjusted and checked day by day.

Minor but important is that it cause CMTS cpu load, as cable network, cisco UBR series especially 7246 has very sentative issue how to handle cpu load. For furture migration network such as MPLS or VPN, additioanl cpu load will be highly required.

Thanks, Gu Sang Jung

[ysj107]

As a engineer(CCIE #12972), I have solved this problem in two approach.

1) Please check your Upchannel Impulse noise not S/N, if there are several time period such as morning or evening, plase check noise source and remove it.

2) I tried to handle above methods, but for me it seems minor beneficial to adjust power level at CMTS side. Some other modem will work same problem at another days. Moreover, if you use and control a lots of CMTS with other operator,it is very hard to control which cell is adjusted and checked day by day.

Minor but important is that it cause CMTS cpu load, as cable network, cisco UBR series especially 7246 has very sentative issue how to handle cpu load. For furture migration network such as MPLS or VPN, additioanl cpu load will be highly required.

Thanks, Gu Sang Jung