VLANs Through POE Phones

[eth_jones]

Just a question - 

 

If I wanted to keep my phones on one VLAN, and my Pc's on another, would that mean that I'm not able to feed my PC's network connection through the phone?

 

I'm sure we've all seen the phones that have two network ports, one for incoming from the switch, and one to carry that over to a PC. If VLAN's are set on a switchport level, does that mean I just couldn't use that feature? Or is there someway that a switch can differentiate between the devices and put out 2 VLAN's from that one port? 

[porina]

The two ports on the phone are usually arranged as a dumb switch. Traffic will flow regardless of VLAN as there shouldn't be any filtering on it. I'm very rusty how VLANs work, but however you set it up you can have different VLANs going through the phone physical connection.

[brwainer]

Welcome to the magic (and hair-tearing frustration) of the “voice vlan”.

 

Assuming your switch has this config option on the ports, here’s how it works:

1) the switch port is set with the untagged or access VLAN being the one you want the computer through the phone to use

2) the switch port is set with a “voice vlan” of whatever you want the phone to use

3) during bootup, before it runs DHCP, the phone will listen for LLDP packets from the switch. The LLDP packets will include the voice vlan.

4) when it sees a voice VLAN in LLDP, the phone will use that VLAN as tagged, meanwhile traffic from its other port is left untagged.

 

Some switches you have to set the voice vlan as being tagged on the port, others you don’t and it is auto-included. Look at your switch’s config guide or user manual for “voice vlan”.