MX67c with phone/PC connected to the same LAN port

[alistairdove]

Hello,

Is it possible to daisy chain a Cisco phone and PC connected to a single LAN port on a MX67c?

I've trawled the internet but as yet have not found an answer.

Many thanks!

[alemabrahao]

MX doesn't support voice VLAN, so I'm not sure if it would work as expected.

Voice VLAN Overview

The voice VLAN feature permits the switch ports to carry voice traffic with Layer 3 IP precedence and Layer 2 class of service (CoS) values from an IP phone. Based on IEEE 802.1p CoS, the switch supports quality of service (QoS) which uses classification and scheduling to send network traffic from the switch. You can configure the Cisco IP phone to forward traffic with an IEEE 802.1p priority, and configure the switch to trust or override the traffic priority assigned by an IP phone.

You can configure the switch port, which is connected with an IP phone, to use one VLAN for voice traffic and another VLAN for data traffic from a device attached to the access port of the IP phone. You can configure access ports on the switch to send Cisco Discovery Protocol (CDP) packets in order to instruct an attached IP phone to send voice traffic to the switch by any of these methods:

In the voice VLAN tagged with a Layer 2 CoS priority value

In the access VLAN tagged with a Layer 2 CoS priority value

In the access VLAN, untagged (no Layer 2 CoS priority value)

The switch can process data traffic which comes from the device attached to the access port on the IP phone. You can configure the switch ports which send CDP packets that instruct the attached IP phone to configure the mode (trusted or untrusted mode) for the access port on the phone.

In trusted mode, the access port on the IP phone passes the traffic from the PC without any change. In untrusted mode, the access port on the IP phone receives all traffic in IEEE 802.1Q frames which contain a configured Layer 2 CoS value. The default Layer 2 CoS value is 0. Untrusted mode is the default.

[alemabrahao]

Usually, the switch and phone use the LLDP-Med protocol to recognize each other. After that process, the switch tells which VLAN to use for the voice and which VLAN to use for data.

More info you can be found here:

https://documentation.meraki.com/MS/Port_and_VLAN_Configuration/Configuring_the_MS_Access_Switch_for...

[alistairdove]

Thanks for the reply. We don't have a switch involved in this setup and was hoping that daisy chaining a phone/PC off a single LAN port might have been possible instead of assigning an individual LAN port to both devices.

[alistairdove · Accepted solution]

Luckily, I've found the answer I was after!

You can either assign the voice VLAN directly on the phone or you can provide DHCP options to push the handset into the voice VLAN to get its DHCP address.

[GreenMan]

What you won't be able to do is power the phone off the MX;   you'll need a PoE injector

[alistairdove]

Luckily, we have power blocks!