How many routers do I need to support 3 vlans over a single ethernet connection

Question

I have multiple rooms each with a single ethernet cable and will have a switch in each room connected to an AP for wireless access on 192.168.?, a teacher workstation on 192.168.2 and one or more student computers on 192.168.3. In the network closet I currently have multiple 24 port switches. I have a single ethernet connection to the WAN. Do I use a single router with multiple configurations of some kind or multiple routers? There will be more than 255 different wireless devices connecting so I'd like for each AP or a group of APs to have/share a subnet. Something like rooms 101-105 on 192.168.10, rooms 106-110 on 192.168.11, etc. I'm assuming the switches support vlans but I can't get to them to check right now.

Is that even possible?

Thanks, Jim.

Answer 1

You can think of a router as a network that connects multiple vlans/networks together.

The number of networks supported by a single router depends on the model. A domestic router might only support two - the internet and an internal network. Though increasingly even a domestic router might support many networks.

If your intention is to connect your networks to the router via a single ethernet connection, then the router must support a vlan trunk - 802.1q tagging. Your switches would also need to support trunking.

This is where each packet is prefixed with the vlan it belongs to as it passes along the trunk (your single ethernet connection) so the devices on each end know which vlan it belongs to.

Answer 2

If you are trying to isolate set of rooms per IP subnets then there are two options either VLANS or just IP subnets routed by a router. As you well point out, VLANS require layer-3 switches. However, as I understand your case it would be sufficient and cheaper to run your network on a simple router with multiple routed Ethernet interfaces, e.g. an Ubiquiti router of the PowerEdge series. In your case you could configure port-1 with IP subnet 192.168.2.x/24 for teacher room and so one Ethernet cable run towards teachers room where you are to have an ordinary switch (layer-2). Then port-2 on the router configured for IP subnet 192.168.3.x/24 for student’s computers and so another Ethernet cable run towards the students’ computer room where you are to have another ordinary switch. The obvious limitation with this approach is that no port on the switch in the student’s computer room would be able to run on the teacher IP subnet. In other words, if in the students’ computer room you would like to run certain hosts on the student network and a certain host on teachers’ network then you would either need an extra Ethernet cable run from the switch on the teacher room to the students’ computer room or you would need to configure VLANs.