I’ve seen people mention this a few times, but I’m not so sure that it’s actually a thing.
Switches are designed to route traffic intelligently, and they don’t blast all of the traffic to every port. If I remember correctly, at some point they do some kind of mapping between IP address and MAC address, and they know which MAC addresses are attached to which ports, and they only route the traffic to the port that has the MAC address they are looking for. I don’t know how much local switches collude with each other to share information about connected devices or how many hops they may be able to look into.
In any event, no matter how wrong I am about that, if you’ve got a device on switch A that needs to send packets to a device on Switch K, then Switch A either has to know that the device is on Switch K and the path to get to Switch K or it has to send the packet to every switch that it is connected to. That doesn’t change with VLAN’s, if Switch A doesn’t have knowledge about every other switch on the network, and which VLAN’s they are configured for, then it will have to send the packet to every switch it is connected to.
FrederikNJS@piefed.zip 2 weeks ago
In addition people often use VLANs for security segregation. For example you might buy a bunch of cheap Chinese security cameras, but want to ensure that they can’t send anything back to the manufacturer. Then you can make a VLAN with no Internet access for the cameras.