Configuring managed switch for VLANs and VoIP

This thread is somewhat stale, but I wanted to clarify this.  I have done multi-vlan tagging on ports for numerous manufacturers of switches and IP Phones.  Recently, I had to learn Dell's way of doing this to accomodate IP Phones (when a workstation is attached to the phone that is attached to a Dell switch).  These comments are not specific to any type of IP Phone - general information only from that perspective.

1 - All switch ports have a default vlan.  This is the "untagged," or "default" vlan.  Cisco refers to it as the "native" vlan.  Dell refers to it as the "PVID" (Port VLAN ID).  HP refers to it as simply, "untagged."  If the switch port is configured as a trunk port, then it will always forward "untagged" frames in the native/default vlan if allowed to do so.  It will also forward frames for any other vlan id's that it receives if configured to do so.  

In Dell's case, the "general" option should be used for IP Phones (that will have PC's attached to the phone).  Dell recommends using trunk mode for uplinks, and general mode for other devices, such as IP phones.  The PVID should be used for workstations and should match the vlan that you want the workstations to boot into, since most workstations cannot mark their own packets.  The PVID is the vlan that will always be used for hosts that cannot tag their frames, or for hosts that do not know what tag to use.

2 - If the switch port is configured as an access port, then anything that boots on that port is forced to be in the vlan assigned to the port.  If the host attempts to tag packets for a different vlan, then the host will never be able to communicate on the network unless the vlan id matches the port's vlan configuration.  With IP Phones, access ports should only be configured for them if they will be the only device on the port.  However, this defeats the advantages that users have to be able to move their phones anywhere in the building and have them work.  This is why we choose to set all PC/Phone ports as trunk ports.  

3 - Anything that boots on a managed switch port is by default in the untagged vlan if it cannot mark its packets.  On your dell switch, you must define the PVID as vlan 100, or workstations will never see the LAN (VLAN 100) through the phone.  The phone will tag its packets with VLAN 200 and the switch will honor this if you use the "switchport general allowed vlan add 200" command.  Also use the 'switchport general pvid 100" command in interface configuration mode to set the "untagged" vlan.  The phone will pass the workstation's frames through untagged so the workstation can communicate on the default network (vlan 100).  The phone must either be statically configured with VLAN 200, or it will obtain this information from DHCP or CDP (CDP capable devices will not work with Dell switches - DHCP must be used.  CDP is Cisco proprietary).