this post was submitted on 07 Apr 2025
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47
Basic networking/subnetting question. (lemmy.dbzer0.com)
submitted 2 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 1 points 2 weeks ago (1 children)

I see, I was completely off-track lol. But isn't this really for a setup where each computer is connected to an individual port of the switch? I.E. this won't work if to one port of an L3 switch one were to attach a dumb 5 port switch and plug 4 computers in

[–] possiblylinux127@lemmy.zip 1 points 2 weeks ago (1 children)

https://en.wikipedia.org/wiki/IEEE_802.1Q

Vlans are simply a tag on a frame. You can set what if any tags are allowed and you can set the switch to tag untagged traffic. You can can limit Mac addresses with port security.

[–] marauding_gibberish142@lemmy.dbzer0.com 1 points 2 weeks ago (1 children)

Thank you. Now I just need to learn to do all of this on Linux/BSD lol

[–] possiblylinux127@lemmy.zip 1 points 2 weeks ago (1 children)

https://openwrt.org/docs/guide-user/network/vlan/switch_configuration

You create an device called interface.vlanid

Something like eth0.1

[–] marauding_gibberish142@lemmy.dbzer0.com 1 points 2 weeks ago (1 children)

Ooh, would it be similar on other Linux distros/Unixes? I'm trying to decide between Debian, VyOS, Alpine and OpenBSD for my main firewall. All of them have strengths but I think it'll be between VyOS and OpenBSD for me.

[–] possiblylinux127@lemmy.zip 1 points 2 weeks ago

Anything that uses the Linux kernel

I would strongly suggest OpenWRT