[c-nsp] Migration from single L2 to multiple VLAN/subnet scenario

[Mark Tohill]

Hi,
 
I have a single Layer 2 broadcast domain comprised of a mixture of access switches from 1900 XL's to 2970's with multiple hosts covering a couple of class C's.  The edge routers have something like the following:
 
int Gigbit Ethernet 0/0
ip address 192.168.10.1 255.255.255.0
ip address 192.168.15.1 255.255.255.0 secondary
<HSRP etc...>
 
I am hoping to upgrade LAN from a physical viewpoint to 2 x 6500's but the addressing needs 're-arranged' so as to reflect multiple Layer 3 VLAN's, probably per customer/application/platform.
 
I'm wondering what the most suitable first step is in this process and would it be best, for example, to create a VLAN (not VLAN 1) to contain all existing traffic covering both subnets i.e a Legacy VLAN. Then, over time, as equipment gets re-addressed, create VLAN's/subnets as required. So the above would get sepeated into two VLANS. With further subnetting, four, and so on.
 
Has anyone ideas on this for an ISP shifting +100Mb traffic?
 
Mark