Hi guys. I'm getting ready to implement VOIP on our LAN. I will have a PRI gateway that takes calls out to the PSTN, so I do not need to worry about WAN issues. I am going to be using non-Cisco, SIP phones, and I will have two VLAN's setup - the native VLAN (10.0.0.0/8) will be used for data, and VLAN 2 (172.16.1.0/24) will be used for voice. The SIP phones have a bridge port built-in that will connect the user's PC to the network. The phones will mark the voice packets with the appropriate DSCP tag, and pass along the data traffic without re-tagging it. The Ethernet drops will run back to two Cisco 2960 switches, that will have trunking enabled on each PC/phone port. A single Sonicwall Pro 2040 will handle routing between the VLAN's.
The question I have is regarding QOS. I know that the "auto qos voip cisco-phone" command forces the port to rely on CDP to detect a Cisco IP phone - therefore, this option will not work for me. I had planned on using the "auto qos voip trust" command on each port, but Cisco recommends using this setting only when a router or switch is hooked up to the port. The only other easy option, that I can see, is enabling QOS globally, and using the default queue settings (buffer, thresholds, etc) that the switch configures. I can then just configure each port to "Trust DSCP", and I will make sure that the DSCP-COS mappings are all set to assign voice traffic to queue 4. My question is whether I should use the modified queue settings that the "auto qos voip trust" command sets, against Cisco's recommendation, or if I should use the default queue settings that are configured when enabling QOS globally. Clearly I want to give the necessary prioritization to the voice traffic, but at the same time I do not want to bring the rest of the network to a halt by using the wrong queue settings.
I hope that I have outlined my situation well enough, but I can certainly provide more details on my config if needed. Thanks for any help that you can provide.