though this post has been sitting here for 2 years. which is a bit sad in reflecting the support of Dell.

I could like to know what is the outcome of this ?

Is the powerconnect 6224's interface port already a layer 3 port ?  or there is some other command similar to "no switchport" i need to execute ?

Thanks in advance

The interfaces on the 6224 switch are considered a switchport interface and not a layer 3 port.  The no switchport command is used to clear any previous switchport associations on the interface.  

In order to set up an IP on the interface you will want to set a switchport mode on the port for a particular VLAN and then set the IP on the VLAN directly.

Example:

console# config

console(config)#vlan database

console(config-vlan)#vlan 10

console(config-vlan)#ex

console(config)#interface vlan 10

console(config-if-vlan33)#ip address 192.168.1.1 255.255.255.0

console(config-vlan)#ex

console(config)# interface ethernet 1/g5

console(config-if-Gi1/0/20)# switchport mode access

console(config-if-Gi1/0/20)# switchport access vlan 10

console(config-if-Gi1/0/20)# exit

Then on your directly connected Layer 3 device you would have another IP address from the same subnet to establish a Layer 3 connection.

Here is a link to the User Manuals available for download

Sorry for leaving this post unanswered for such a long time.  

I hope this helps,