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Aspiring Contributor
Message 1 of 4

Multicast "flooding" LAN side of Router

I will admit that I am not 100% sure whether this is a multicast issue or not however, this was how a neighbour friend of mine explained the issue and it seemed plausible.


The issue is that I am randomly losing internet connection (Infinity 2) across my LAN yet I do not across WiFi.


My set up:

To the router (Home Hub 5), I have a BT TV youwview+ box directly linked and then I use PowerLines (Solwise 1200Mbps AV2) to hard wire to a multitude of devices around the house including a second youview+ box. Therefore I am only using 2 of the router ports with the Powerlines supporting about 10 other devices (Smart TVs, NAS, PC, printer, etc).


The issue:

Since having the second youview+ box, there has been random drop out of the internet connection but only on the LAN side; the WiFi continues to work without issue.  It is not only on the devices connected over the powerlines but also the BT TV box connected directly to the router.  The only way to resolve is to turn off the router and powerlines for at least 15 minutes.


Possible explanation offered:

The way in which multicast is being delivered to the property is flooding the LAN side of the router and the router cannot cope with that amount of data/traffic.


Is there any other explanation and/or possible solutions to the issue?


BT's customer service team solution was to send an engineer at my cost for what is a random issue and might or might not occur when the engineer is at the property...

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Aspiring Contributor
Message 2 of 4

Re: Multicast "flooding" LAN side of Router

Very kind of someone to move my post to this part of the forum without notifying me, making me think that it had been deleted...


...Are there any multicast experts out there that can confirm or discount this as the reason for the LAN side of the router dropping out periodically?


It's a very fustrating experience to reboot all the powerlines and router on a regular basis.  Especially when the youview boxes are not even in use.

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Aspiring Expert
Message 3 of 4

Re: Multicast "flooding" LAN side of Router

@HairyHippy you could use WireShark to monitor network traffic and check to see if multicast packets are being delivered/flooded to your PC.

If you're getting a ton of multicast packets at your PC then that's likely the issue as the Hub should be making sure only the IPTV devices receive them.
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Aspiring Contributor
Message 4 of 4

Re: Multicast "flooding" LAN side of Router

WireShark is what the neighbour also suggested, now need to learn what it's telling me...  I've since installed this software and was monitoring traffic on the PC but the amount of data it was returning (primarily between NAS and PC across the same ethernet switch) I'm struggling to interpret.


However, as @adly implies the Hub should be intelligent enough to only send multicast to IPTV devices...  Therefore I would expect that the BT TV box connected directly to the HH as described in the opening post would continue to work fine (it doesn't)... The HH would therefore potentially "flood" the powerline as would be trying to send muliticast to the second box across the powerline thus it would be down to the powerline adaptor to know which devices need IPTV???


So again, the entire side LAN side of the router disconnects; WiFi works perfectly fine.  Is it because the router (HH5) doesn't know how to direct multicast?  Concluded because the BT TV (youview+) box directly connected to router also cannot "connect".  Or is there another reason the LAN side of the router is dropping out and multicast is a misnomer?


Thanks for your reply @adly however, I am failing to understand that if the HH has the intelligence to only deliver multicast to the IPTV enable devices, the the box directly connected to the router should be unaffected.

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