Hi all

I have a question about VLAN tagging

I have configured 3 VLAN's on a Dreytek Vigor 2860 router with the following tags

10 (Data for staff - accessing from computers on ethernet and wireless)
20 (Data for public (not staff) - wireless connections only)
30 (Voice - VOIP)

I have also configured the default gateways and ip ranges for each VLAN
10 - 192.168.10.X
20 - 192.168.20.X
30 - 192.168.30.X

How does the router know which VLAN should be used for allocating an IP to a device. For a computer and Mitel phone for example. I am aware that with the exception of hypervisors, other devices such as computers, laptops and phones, are not VLAN aware. I have read about the TPID -TAG Protocol Identifier and the first 4 bytes are made of the VLAN TAG, however do not understand how the packets are indentifed for VLAN allocation unless the packet is marked or identified based other characteristics.

Kind regards

Matthew

You really need a dot1Q aware managed switch in-between the router and devices.
If not then you might as well just do port based VLANS if you are plugging directly into the Draytek

Hi Sicon

Thanks for your reply. We will be using switches with IEEE 802.1Q which we understand supports VLAN tagging. I just wanted to understand how packets are distinguished and subsequently marked with a specific VLAN tag.

For example

Staff connecting via ethernet and WIFI on a STAFF SSID
Residents connecting via WIFI on Residents SSID
VOIP phones

Kind regards

Matthew

They are tagged by the switch port that uplinks to the router.

In your case the 3 VLANs wold all be tagged on the switch port that links the router (if you only have 1 uplink to the router that is)

The ports in each VLAN that laptops/PCs/Servers connect to would be untagged within the specific VLAN except things like Access points.


You need to create Voice Specific VLANs for Voip

If you do some searching I'm sure I have put pictures up of VLAN configs before

Hi

I understand with basic port specific VLAN's it would work like this:

Router Port 1 - VLAN: 10 > connected to switch 1 - Staff device
Router Port 2: VLAN: 20 > connected to switch 2 - Resident device
Router Port 3: VLAN: 30> connected to switch 3 - VOIP

If we scrap the above and use VLAN tagging for all VLANs and apply all of VLANS on all ports on the router, how does the switch know which packet is for what VLAN?

Assuming you are leaving the default VLAN and want everything to go via LAN1 it would look like this



The Switch will also need the 3 VLANS with the port that uplinks the switch TAGGED in EACH VLAN.
An untagged port can only be in 1 VLAN this is how it knows



If you plug a Laptop into Port 2 abve you will get an address form VLAN2
If you plug a Laptop into Port 3 abve you will get an address form VLAN3
If you plug a Laptop into Port 4-12 abve you will get an address form VLAN4