VOIP through 2960 L2 Switches/ASA

[Nicholas Beard]

Chaps,

I currently have 6 switches, 2 x 2960G are the distribution switches and 4 x 2960 as the access switches, each of the access switches have redundant 2GB uplinks.  I currently run only 2 VLAN's (which span end to end unfortunately) through the switches and need to add an additional voice VLAN.  Due to the limitation of the Layer 2 switches i need to route the VLAN through an ASA 5510 (not ideal).  The current data VLAN's are 10 and 100 with the latter being for management traffic only.  I am looking to create a VLAN 20 to carry voice from 8 x IP phones.

Firstly, would it be best to plug the IP phones directly into the distribution switches as they directly connect to the Cisco ASA, as i am aware the redundant uplinks to the distribution switches from the access switches are only 2GB and are carrying all data as well?

Secondly, what would be the best configuration for the ASA?  Would i need to create a trunked physical interface and then split this into sub interfaces tagging the individual VLAN's?  Or, would it be better to use physical interfaces on the ASA, one for the data and one for the voice?

Thirdly, I am aware of the configuration required for QOS on the switches; if the IP Phones are plugged into the access layer, will I need to also add QOS settings to the trunked uplinks into the distribution layer?

Lastly, are there any QOS settings required on either the sub or physical interface configured on the ASA?

Many Thanks

Nick

[Fabienne Stephanoff · Accepted solution]

Hello Nick,

Let me address the LAN-Switching questions you have.

You will need to hit the security community for any ASA specific configurations.

Would it be best to plug the IP phones directly into the distribution switches as they directly connect to the Cisco ASA, as i am aware the redundant uplinks to the distribution switches from the access switches are only 2GB and are carrying all data as well?

Answer: Voice traffic is normally low bandwidth so you should be fine connecting them to access layer switches as long as your qos configurations are correct on all ports the voice traffic is traversing.

I am aware of the configuration required for QOS on the switches; if the IP Phones are plugged into the access layer, will I need to also add QOS settings to the trunked uplinks into the distribution layer?

Answer: Yes you will need to add qos on the trunks between switches to make sure the voice traffic is prioritized end to end, I would recommend you use "auto qos voip trust" and "priority-queue out".

You can paste your sample voice/trunk port config and I'll review for you.

Hope this helps.

Fabienne