I've inherited a moderate size network that I'm trying to bring some sanity to. Basically, its 8 public class Cs and a slew of private ranges all on one vlan (vlan1, of course). Most of the network is located throughout dark sites.

I need to start separating some of the network. I've changed the ports from the main cisco switch (3560) to the cisco router (3825) and the other remote switches to trunking with dot1q encapsulation. I'd like to start moving a few select subnets to different vlans.

To get some of the different services provided on our address space (and to separate customers) on to different vlans, do I need to create a subinterface on the router for each vlan and, if so, how do I get the switch port to work on a specific vlan? Keep in mind, these are dark sites and geting console access is difficult if not impossible at the moment. I was planning on creating a subinterface on the router for each vlan then setting the ports with services I want to move to a different vlan to allow only that vlan. Example of vlan3:

3825:

interface GigabitEthernet0/1.3
description Vlan-3
encapsulation dot1Q 3
ip address 192.168.0.81 255.255.255.240

the connection between the switch and router:

interface GigabitEthernet0/48
description Core-router
switchport trunk encapsulation dot1q
switchport mode trunk

show interfaces gi0/48 switchport

Name: Gi0/48
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

So, if the boxen hanging off of gi0/18 on the 3560 are on an unmanaged layer2 switch and all within the 192.168.0.82-95 range and are using 192.168.0.81 as their gateway, what is left to do, especially to gi0/18, to get this working on vlan3? Are there any recommendations for a better setup without taking everything offline?