Hi

So many questions!

The first config and second config examples are the same, except the first also has QoS configured on it. These configurations are suitable for links between switches, all VLANs will be carried accross as they are configured as trunks.

The third config is an edge port config, but not a great one as you've discovered. In the middle ages it was normal to configure the edge ports as dot1q trunks to allow the phones to get into a different VLAN to the PC that was attached to the phone, but that's not what you would do now. A more suitable port config would be:

int x/x

switchport mode access

switchport access vlan X          <--- whatever VLAN you want for the PC

switchport voice vlan Y          <.--- VLAN for the phone

auto qos voip cisco-phone     <--- see below

spanning-tree portfast                < start the port quickly rather than going through full STP process

In terms of QoS, DSCP, etc... there's lots to know here. If you're new to QoS, set 'auto qos voip cisco-phone' on your edge ports, and 'auto qos voip trust' on all inter-switch links, and then read up on it! There's lots of info on the Cisco web site...

Essentially once you do this you will have a network that runs on CoS markings. CoS is a field in the dot1q or ISL header found on trunk or Voice VLAN enabled interfaces.

DSCP is a field in the IP Header that is more granular, and has the advantage of being present on all IP packets whether traversing a trunk link or not.

There are maps on the switch that will rewrite each of these fields based on configured settings - these settings are applied to the switch the first time that you enter an 'auto qos' command on a port, so you don't have to get too hung up on it for now.

Regards

Aaron

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