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sbstnceovrstyle
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Why Would an Offline Modem Also Disconnect Wifi?

The subject says it all.

I am new to Virgin (I arrived in the UK on March 8 from Australia).  In all my experience with cable and ADSL modems when they aren't connecting to the ISP they still always keep the WiFi active enabling all wireless devices to remain connected to WiFi even if the modem doesn't have internet.  Why do both the first modem I was issued with and the second both go offline for WiFi? (The two were the same model).

I am in South Kensington and there is a utilisation issue here (too many people using the network) and I have had no reliable service since when I signed up.  I have been told that it's going to take until July for me to see this issue resolved (nobody at Virgin is getting too upset about it - it seems to be just one of those things for Virgin - nothing to lose sleep over).   I want to provide my computer help businesses' remote customers with support and the internet doesn't stay up.  Apparently there was a known issue in my area when I signed up but the person who signed me up on the phone never said anything about it.

There are two things about my circumstances which are all pretty disgraceful:

1.  I was signed up without being told of the issue in my region.

2.  It's going to take until July to fix.

3.  I have to be the one to call up and ask for a credit on my bill.

Anyway, it would at least be nice if I didn't have to manually connect each of my devices to WiFi when a disconnection happens (tonight it's gone offline about five times).

Philip

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Superuser
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Re: Why Would an Offline Modem Also Disconnect Wifi?

Because these all-in-one hubs are essentially one motherboard with a core CPU such as Puma 5 or Puma 6 SoC, with wifi and router chips on the same board, resetting the core CPU tends to reset the wifi too.

superhub3-architecture.png

 

In order to avoid losing wifi, buy a 3rd party router and put your hub into modem mode.

Then your wifi network will continue to work independent of the modem/hub.

In your situation I would suggest buying a router such as an Asus RT-AC3200 which has Dual WAN and 3G/USB features. These will allow you to provide failover capability from a second broadband or mobile connection in the event that the Virgin hub loses internet.


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Superuser
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Re: Why Would an Offline Modem Also Disconnect Wifi?

I have 5 different models of cable modem from 3 different manufacturers. They all work the same way, as they're designed to follow the DOCSIS specification.

SH1, SH2, SH2ac all from Netgear, Hub 3 (Arris), Hitron CGNv4.

The wifi resets when the modem needs to go through the full cable modem registration & ranging process to acquire a full set of channels.

The modem resets when it has not received an opportunity to communicate with the CMTS (big modem at VM's end) for 30-35 seconds, as would happen when the cable connection is under high utilisation. See T4 timeout: https://volpefirm.com/docsis_timout_descriptions/

If the modem can't acquire the set of channels and/or can't communicate properly with the CMTS again, then it'll go into repeated resets. Thus your wifi will go off and briefly on and off again while the firmware goes through the 2 minute boot-up and registration process over and over.

This is the extreme situation.

 

There are less extreme situations where you get disconnected briefly for a few seconds, like in a T3 timeout, but the modem does not have to reset. Same with SYNC or MDD timeouts on the downstream. In these cases the wifi stays on. If only one or two channels are lost the modem goes into partial service mode but continues on without reset as long as it can.

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Superuser
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Re: Why Would an Offline Modem Also Disconnect Wifi?

Because these all-in-one hubs are essentially one motherboard with a core CPU such as Puma 5 or Puma 6 SoC, with wifi and router chips on the same board, resetting the core CPU tends to reset the wifi too.

superhub3-architecture.png

 

In order to avoid losing wifi, buy a 3rd party router and put your hub into modem mode.

Then your wifi network will continue to work independent of the modem/hub.

In your situation I would suggest buying a router such as an Asus RT-AC3200 which has Dual WAN and 3G/USB features. These will allow you to provide failover capability from a second broadband or mobile connection in the event that the Virgin hub loses internet.

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Superuser
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Re: Why Would an Offline Modem Also Disconnect Wifi?

Btw, sorry to advise you that the date you have been given is only an automated review date. When the date comes it will be pushed forward by 3 months and so on, until the work actually happens. Often takes around 6 months before they try to add additional downstreams to improve an over-utilisation situation. Can take up to a year to resolve, or longer in some cases.

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sbstnceovrstyle
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Re: Why Would an Offline Modem Also Disconnect Wifi?

What an awesome answer!  Thank you MUD_Wizard

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