VLAN device, Trunk port, and DHCP?


#1

I have my Balance One set up with two VLANs, the default un-tagged one and a guest network on 1003 (which is over wifi via an Airport Extreme).

I have a Cisco 525G VOIP phone which I want to run on the guest VLAN. I could do this over WiFi easily, but I prefer to hardwire it on Ethernet, and I’d like to avoid running more ethernet cable.

Assuming I set the phone up properly (it has built-in VLAN support):

  1. Can I plug the phone into a switch hanging off of the regular (untagged Trunk) ethernet port?

  2. Assuming the answer to 1 is “yes”, when the phone pulls a DHCP address, it should pull it from the VLAN DHCP range, right?

Apologies if these are stupid questions but I’m new to VLANs…


#2

VLans work by “tagging” bits of data called packets. It sounds like your phone can do the tagging for you. The numbers mentioned next are all variable, you can pick what you want.

Step 1 configure the phone to tag its VLan to 10. VLan10 will be what it tags it’s packets with.
Step 2 configure the VLan in the Peplink. Search the forums - there are lots of examples. Just make sure that the number matches what you did in step 1 (10)
Step 3 configure port types in the Peplink. Whatever port you are going to plug the network wire into must allow traffic for VLan10. You change the port to Trunk, custom, then select the networks that are allowed. Vlan10 should be at least one of the entries. I typically always leave the local LAN on all trunks. This is preference or security driven decision.

The phone should now pull an address from the vlan10 dhcp pool.

The advantage of having the phone “tag” the traffic is that you can have a link from a switch to the Peplink that has no clue about VLans. You can plug the phone into the switch and still get the right address. If you don’t tag the traffic at the phone, you are dependent upon a device between you and the Peplink to tag your traffic for you (or the Peplink can do it - that is an Access port type). If Peplink does it - any device that is connected to that port will be on vlan10. Switches can have VLan support and tag traffic too - they are called “smart switches”.

Hope this helps and have fun with those VLans. For what it is worth - you most likely don’t have to do anything but plug the phone in and it work, you probably don’t have to mess with VLans at all. Segregating the phone shields it from network chatter from the other devices on the main LAN (untagged). You would do this (vlanning) if you had performance issues or wanted to do special network shaping/routing.


#3

Thanks. I tried it and it works great: The phone does the VLAN tagging and it properly pulls the DHCP address from the VLAN subnet, even though it’s plugged into the normal ethernet switch.