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Beginner

what are the reasons why a wideband modem can not take a CPE?

I have an M-CMTS with RFGW1.

I have the following settings:

int c6/1/3

downstream Modular-Cable 1/0/0 rf-channel 16-17 upstream 0-3

int c6/1/4

downstream Modular-Cable 1/0/0 rf-channel 18-19 upstream 0-3

cable fiber-node 9

  downstream Modular-Cable 1/0/0 rf-channel 16-19

  downstream Cable6/1/3

  upstream Cable 6/1 connector 12-15

cable fiber-node 10

  downstream Modular-Cable 1/0/0 rf-channel 16-19

  downstream Cable6/1/4

  upstream Cable 6/1 connector 16-19

interface Wideband-Cable1/0/0:4

load-interval 30

cable bundle 1

cable bonding-group-id 5

cable rf-channel 16 bandwidth-percent 45

cable rf-channel 17 bandwidth-percent 45

cable rf-channel 18 bandwidth-percent 45

cable rf-channel 19 bandwidth-percent 45

----------------------------------

the cable modem gets online, but does not take cpe, my question is why?

D2.0 modems do take CPE, but the 3.0 modems do not. I know that may be a problem in the RFGW1 because another time I changed the port and it worked.

but I would like to know the reason why only the wideband modems are not taking cpe.

I'd like to hear from you.

thanks in advance

Everyone's tags (5)
3 REPLIES 3
Cisco Employee

what are the reasons why a wideband modem can not take a CPE?

Hello Diego,

Hope you are doing good. When you say the CM doesn't take CPE, what do you exactly mean? Is the CPE not able to get an IP address via DHCP? It is getting IP address but it doesn't have connectivity?

For the reasons why it may be affectin only WB modems, it could be that D3.0 modems are using the remote (Modular) channels, which go through the RFGW1 to connect to the network. From the portion of config you provided I see that you are also using the local DS channel from the LC which is probably being used by the D2.0 CMs. If this is the case, and there is some issue with the remote channels, then you may see only D3.0 modems affected.

Best regrads.

Beginner

what are the reasons why a wideband modem can not take a CPE?

Thank you! Manuel

When I said that I did not take the CPE modem, I meant that the CPE was not getting an IP address from the DHCP. But after doing several tests we saw the following:

- The first time that was put online, it became as w-online and take CPE (The DHCP assigned IP addresses both, Modem and CPE)

- But it did not work, so I reset the modem, and went online again, (but did not have a CPE IP address)

- When doing a ping test to the modem, did not get any response.

- Then change the port and RFGW1 and everything worked.

What I still do not understand is that the modem being w-online and got an IP address, no response was obtained in the Ping.

I also want to mention that we have online D2.0 modems on modular interface (Mo1/0/0: 16), which comes from RFGW1, and these did work properly.

Once again thank you.

Cisco Employee

what are the reasons why a wideband modem can not take a CPE?

Hi Diego,

- The first time that was put online, it became as w-online and take CPE (The DHCP assigned IP addresses both, Modem and CPE)

- But it did not work, so I reset the modem, and went online again, (but did not have a CPE IP address)

I'm not following you here. In the first point you mentioned that the modem came w-online and the CPE got an IP. However, in the second point, you mentioned that it didn't work and then you reset the modem. What didn't work (I understood the problem was CPE getting IP address which, as you mentioned, was done on the first point)?

You also said that, at some point, the modem was online but not pingable. The CPE didn't get IP that time. In that case, was the modem online or w-online? What was the primary channel for this modem? Take into account that, for wideband, the modem uses the primary channel to register and perform all Docsis operation. Any data traffic (like a ping or a DHCP request from a CPE) will use the secondary channels. If these channels have some issue you may see an issue as the one described.

For the D2.0 modem using Mo1/0/0:16, it could be similar as above. If this channel is OK but the rest have some issues, you could see a behavior like that. The D2.0 modem will use the primary channel (only channel) also for data transfer. Since this channel is OK, the D2.0 modem don't have any issue. However, if a D3.0 modem uses Mo1/0/0:16 as primary it may come online (since the channel is OK) but, if the rest of channels have issues, then you may have problem to pass data traffic.

Did you check if D2.0 modem can use all the channels? You may also want to check the modulation profiles being used. It could be that you are using a lower modulation profile for ranging (initial, station maintenance) and a higher one for data transfer which may be affected by some condition in the network.

Best regards.

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