Understanding Vlan setup

[bilbotel]

Can someone clarify how based on the below phones get an ip from mitel and computers from separate dhcp server and dont get the wrong ip when connected to the same port. I assume it is controlled by the switch and by virtue of the fact that vlan3 is tagged as voice and the mitel server is connected to a vlan3 only port?
extract:

Code: [Select]

ip subnet-zero
ip routing
!
!
mls qos
!
!
no file verify auto
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending

interface FastEthernet1/0/2
 description Connection to Mitel 3300ICP
 switchport access vlan 3
 switchport mode access
 priority-queue out
 mls qos cos 5
 mls qos trust cos
 spanning-tree portfast

!
interface FastEthernet1/0/3
 description Data and Mitel Voice
 switchport access vlan 2
 switchport mode access
 switchport voice vlan 3
 priority-queue out
 mls qos trust cos
 spanning-tree portfast
interface Vlan1
 description Management VLAN
 ip address x.x.x.1 255.255.255.0
!
interface Vlan2
 description Data VLAN
 ip address 111.22.333.1 255.255.255.0
 ip helper-address 1.2.3.4
 ip helper-address 5.6.7.8
!
interface Vlan3
 description Mitel Voice VLAN
 ip address 192.168.1.1 255.255.255.0
!
ip classless
ip route 0.0.0.0 0.0.0.0 100.0.0.100
ip http server
!
Mitel:
Confusing me is that in system ip on the mitel voice is vlan1
Layer 2 switch voice vlan 1
DHCP subnet name voice vlan  192.168.1.0
DHCP Range specifies voice vlan  192.168.1.0
DHCP options 125 does not specify a vlan, that field is blank, it only includes tftp and call server.

Many thanks

[lundah]

The phone identifies itself as a phone when it boots up and starts communicating with the switch, so the switch assigns the phone to the voice VLAN instead of the default/data VLAN.

[bilbotel]

So its down to the switchport mode voice vlan 3 command in essence and the vlan options on the mitel dont come into it in the above scenario?

[Dogbreath]

Correct. Mitel is in access VLAN 3, i.e. it does not know that there is a VLAN.
CDP or LLDP-MED frame from switch tells handset that there is a voice VLAN and handset tags its own  frames accordingly. Switch un-tags frames before sending them to Mitel.
You could make the Mitel VLAN-aware [so it tags its own traffic] but you won't be solving any problems that I can think of.