Large school, Multiple Chromebooks & connectivity issues

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John Weir

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May 24, 2022, 5:25:17 AM5/24/22
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Hi all,

I am looking to connect with some schools who would be using a large number of chromebook devices. 10 weeks ago we changed over to a fibre connection and since then have had daily issues of broadband dropping when multiple chromebooks try to log in simultaneously. We have been fully engaged with PDST throughout this time and to their credit they are hard on the case. 

I won't bore you with the litany of troubleshooting but in short the finger of blame seems to be narrowing down to the fritz modem  ( 7530 model) being unable to handle multiple logins (60 - 70 simultaneously). One possibility is that there is a function or config issue on that modem that the old Fritz 7360 (which we used before the change to fibre) did not have.

Another area being considered is how the Chromebooks talk to each other. They seem to use P2P automatic updating. This in turn floods a network with multicast DNS requests. The more Chromebooks that come online, the more mDNS requests are sent and the more you suffer a problem. 

I was looking to connect with any other large schools (it probably would be in the secondary sector) with multiple chromebooks on a fibre connection to see if we are doing something different or have a different network setup.

many thanks,

John

Mark Delahunty

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May 24, 2022, 6:07:17 AM5/24/22
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Hi John,
We had the same issue. It was due to our upload speed. We had to install a second line to handle the demand.
Regards,
Mark

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Cóilín Ó Coigligh

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May 24, 2022, 6:39:11 AM5/24/22
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Hi John,
Have you a third party firewall in front of your fritzbox?
Our IT man is in today and this is what solved it for us. I have shown him your email if you want to give him a call.
Seán Carolan, Tantach, 083-4205405
Tantech are a Google partner.
Beir bua
Cóilín

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Cóilín Ó Coigligh
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Mark Delahunty

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May 24, 2022, 6:39:12 AM5/24/22
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Also John we had to get a larger number of ip addresses. As this was also causing connectivity issues. An easy way to identify this is to count up the number of devices connecting to the network at any given time including teacher phones, tablets etc and see if this is greater than the number of ip addresses you have on your network. 
Regards,
Mark

Áine Uí Choinne

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May 24, 2022, 7:09:21 AM5/24/22
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John, we had the same problem here-we bought 30 chromebooks , in additional to what we had (PC, laptop, teachers phones, printers etc) and we couldnt have more than 19 or so connected at once. We installed a new router, €200 plus €200 for installation, a cheap enough fix, and now we have added 30 more chromebooks for the Junior side, and no connection problems at all. Hope that helps. 
Áine Uí Choinne , Gaelscoil Dhún Dealgan 

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Val Gavin

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May 24, 2022, 8:09:19 AM5/24/22
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Morning John
Just a question, are you using public IP addresses and if so how many have you been allocated, if public then you may have reached your allocated lot
Check with pdst.

You can email or call me offline anytime.

Val

Val Gavin Computer Services
0872671234 


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Liam Onofrei - Ctrl Alt Del

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May 24, 2022, 8:28:18 AM5/24/22
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Hi John,

 

Thanks for sharing.

 

I don’t think is the IP or asymmetrical speeds or CAT5 vs CAT6 related issues…

 

You have identified one of the bottlenecks: local broadcast, multicast traffic, mDNS or Bonjour.

Use the Wireshark and you will be shocked how much of your local traffic is non user generated noise but rather device to devices…

And is valid for both Google and Apple devices, designed to operate at home, in a smaller home network.

 

I will highly advise in to looking at network segmentation and / or VLANs.

The implementation of VLANs is not supported by PDST routers so you will need to apply some ”pen and paper” to create a segmented IT architecture.

 

Contact your IT Consultant and request a meeting to discuss the new approach in respect to network design.

 

Good luck and enjoy IT.

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