Multicast Flooding by Steam Client

[Bear]

1. from time to time my ISP blocks (automatically) my ip address due to "multicast flood"
2. this may be due to torrent-like programs trying to find peers on the local network
3. we did an investigation with my ISP's tech support and found that "multicast flood" occurs when downloaded by the steam client (not other programs)
4. I can't change ISP and would like to continue using Steam
5. i need to change the settings of the steam client so that it does not search the local network, but I did not find such a setting in the current version of the steam client (I think it was before)
6. help me set up the steam client correctly

i wrote to steam support but they send me useless answers «not us problem»
sorry for my bad english

[Joke]

Maybe it's the new option that allow users to download from other users that is causing your problems?

In the Settings Dialog, choose the Downloads page, and then look at the last dropdown.
It controls who can download from who, and one of the options is to turn the function off.

[Ettanin]

Yes, you should turn this option off because your ISP's CGNAT looks like a LAN to Steam.

This can happen if your ISP doesn't use 100.64.0.0/10 (as specified in RFC 6598) but uses RFC 1918 addresses instead.

[Elucidator]

This should have the information you need:
https://help.steampowered.com/en/faqs/view/2EA8-4D75-DA21-31EB

You need to set up your routing table so that they only search the gateway (WAN), rather than your local area.

Your internet access provider can do it from their own side by configuring the router: (outbound traffic from client to WAN, etc.) but if they refuse to do so then you will need to do it locally.


Edit: just saying, but it is to be expected that end users will use services that will by default multicast, including Torrent services and other p2p stuff.
I think your ISP sucks if they start blocking that, unless.. its a private company's own internet access service.
but like, for a home user, its foolish. They're going to get a large sum of complains. (unless they preconfigured everything to just search the gateway rather than other clients)

Just imagine someone with a family with multiple pcs, or a net cafe or something...
and they can't download from their own LAN, because ISP nonsense. sigh-

Also windows 10 and windows 11 both have 'download updates from eachother' (rather than just microsoft services), which also creates a mesh network source to download from, which also requires multicasting. World most popular OS at the moment may get blocked for that reason.

[Bear]

Originally posted by Joke:

Maybe it's the new option that allow users to download from other users that is causing your problems?

In the Settings Dialog, choose the Downloads page, and then look at the last dropdown.
It controls who can download from who, and one of the options is to turn the function off.

thank you, early i dont see this setting, now its work!