Voice and data on Catalyst 2950C

[tony.h]

IOS:c2950-i6q4l2-mz.121-22.EA1.bin

Configuration:

interface FastEthernet0/2

description IP Phones&PCs

switchport mode access

switchport voice vlan 200

mls qos trust device cisco-phone

mls qos trust cos

no snmp trap link-status

auto qos voip cisco-phone

spanning-tree portfast

end

If I configure the phone to Vlan 200, the phone can pick up the DHCP address for phone.

The pc connected to phone can pick up DHCP address for data.

Could anyone please advise why and how?

Thanks,

Tony

[Aaron Harrison]

Tony

The switchport voice vlan 200 command instructs an IP phone that you plug into the port to work in VLAN 200 by a CDP exchange at startup... You shouldn't actually have to configure the VLAN on the phone yourself..

The PC attached to the phone will go into the normal vlan for the port which in this case will be 1 as it is left at default...

Basically the link between the phone and switch is a dot1q trunk.

[tony.h]

Thank you for your reply. I try the following commands:

interface FastEthernet0/2

description IP Phones&PCs

switchport mode trunk

no snmp trap link-status

spanning-tree portfast

end

The phone still picked up data vlan IP address.

IP-Helper has been configured and works on 3560 and 3750 where I use the following configuration:

mls qos

interface f0/2

sw mode acc

sw voice vlan 200

mls qos trust cos

Could you please provide a working configuration? Your help is really appreciated.

Thanks,

Tony

[markanthony]

What does your trunk configuration look like on the 2950 and on the router that is connected to the 2950? Are you aloowing only certain VLAN's? How about if you configure a port on the 2950 to native VLAN of 200 and see if a PC connected to it gets an IP from VLAN200. What kind of link is between the 2950 and the other switch?

What do you see in your logs if you do

debug ip dhcp server events

debug ip dhcp server packet

[tony.h]

The topology is as below:

IP Phone 7940<-->2950<---trunk--->3750<---(IP networks)-->CallManager

If I place the port under vlan 200, the phone works.

There is no problem with DHCP. It seems there is something missing or wrong.

[markanthony]

also remember that you still have to use the ip helper in your VLAN200 on the layer 3 switch if your DHCP server is not in there so that it can forward the request for the DHCP address.

[Aaron Harrison]

Tony

I've just re-read your original post, I may see the problem now...

You say that if you put the port in access vlan 200 the phone works fine? Then your ip-helper/DHCP/other trunk ports must be set up OK.

On your original post, you said you had this config:

interface FastEthernet0/2

description IP Phones&PCs

switchport mode access

switchport voice vlan 200

mls qos trust device cisco-phone

mls qos trust cos

no snmp trap link-status

auto qos voip cisco-phone

spanning-tree portfast

Try this configuration but without the 'switchport mode access' - you can put in 'switchport mode dynamic auto' instead.