this post was submitted on 07 Apr 2025
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Basic networking/subnetting question. (lemmy.dbzer0.com)
submitted 3 weeks ago by marauding_gibberish142@lemmy.dbzer0.com to c/selfhosted@lemmy.world
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Sorry for being such a noob. My networking is not very strong, thought I'd ask the fine folks here.

Let's say I have a Linux box working as a router and a dumb switch (I.e. L2 only). I have 2 PCs that I would like to keep separated and not let them talk to each other.

Can I plug these two PCs into the switch, configure their interfaces with IPs from different subnets, and configure the relevant sub-interfaces and ACLs (to prevent inter-subnet communication through the router) on the Linux router?

What I'm asking is; do I really need VLANs? I do need to segregate networks but I do not trust the operating systems running on these switches which can do L3 routing.

If you have a better solution than what I described which can scale with the number of computers, please let me know. Unfortunately, networking below L3 is still fuzzy in my head.

Thanks!

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[–] marauding_gibberish142@lemmy.dbzer0.com 0 points 3 weeks ago (1 children)

It's not that they are expensive, it's that they run archaic proprietary OSes which the consumer cannot control. I cannot trust such a switch when the rest of my network depends on it. Please let me know if something in the post didn't make sense.

[–] cmnybo@discuss.tchncs.de 2 points 3 weeks ago (1 children)

Put a multi port NIC in your router PC and use a separate unmanaged switch for each network then.

[–] marauding_gibberish142@lemmy.dbzer0.com 0 points 3 weeks ago (1 children)

Thanks but as I mentioned that will not scale. I'm interested in if separating computers by subnets will work. Have you tried something like this?

[–] Pogogunner@sopuli.xyz 2 points 3 weeks ago* (last edited 3 weeks ago) (1 children)

It's been a long time since I actually used subnets, but IIRC you will need a physical interface for each network on the router regardless.

So let's say you set up your /24 network into 2x /25's, you will need an interface for the .0 network, and another for the .128 network

If you just have an interface for the switch, and another for the WAN connection, I don't think subnetting will work for what you're trying to do

[–] marauding_gibberish142@lemmy.dbzer0.com 0 points 3 weeks ago

Hmm, so virtual interfaces on the router won't work? I admit I'm a bit stumped, would you be able to give me an ELI5 on why this is the case? I will try and read up more, of course