Can you run a VoIP phone and a PC off a routed interface?

[Venison Mogambi]

We have a situation where we're connecting a user directly to a routed interface on a Cisco 2921 and the user has also requested a Cisco VoIP phone. Normally you would put the VoIP phone on a switch and set the switch port up for both Voice and data VLAN access. But in this particular case we're not able to deploy a switch (or a switch module) - basically we're stuck with the hardware we have. So is there a way to host both the VoIP phone and the user's PC off of the routed interface?

I did have one idea for this...the phone is technically a two-port switch, correct? So could we treat the connection to the router as a trunk and configure subinterfaces on the interfaces for the Voice and Data VLANs? 

Any suggestions are appreciated.

Thanks! 

[Ayodeji Okanlawon]

The simple answer to this would be NO. You need a trunk port on a switch port to carry multiple vlans. Hence when you configure voice vlan and access vlan on a switch you essentially make it a trunk port.

Your sub interfaces on a router is not a trunk port. Its used for routing between vlans. These rae two very different things..

[Mohammed al Baqari]

Hi,

On the phone, navigate to network settings and scroll down to 'Admin VLAN', select edit key and assign Voice VLAN. This VLAN will be used by the phone to tag voice traffic. The data traffic won't be tagged.

On the router create a sub interface for admin vlan (voice vlan) and assign the data vlan to main interface (or create another sub interface with native vlan).

I haven't tested this before. But from the concept level it should work.

[Venison Mogambi]

Thanks for the feedback. I guess the answer is maybe yes, but probably not?

In theory, it seems like it should work - a switch that is trunked to a routed interface on a router tags and carries multiple VLANs and those VLANs are routed on the subinterfaces (i.e. router on a stick). But the connection from a Cisco VoIP phone may operate differently than a trunked link from a switch.

I'll continue to investigate and update if I find any interesting info on this.

[mikeleebrla]

Why are you trying to put the data and voice separate VLANs/networks? The phone will work fine on a simple "access" port on a switch. In a large environment you usually put data and voice on separate VLANs to segregate the traffic, but in this case we are only talking about two devices (PC and a Phone).