Hi perpaal
Separating the Network Traffic into different VRFs depends upon our choice and we need to consider whether the segregation is required on just 1 device which terminates the traffic or the traffic separation is required all across the Backbone..Typically we achive the traffic separation via VLANs which restricts the broadcast domain of a particular traffic type we associate to the VLAN. Still the VLANs can communicated to each other via Inter-VLAN routing on same device and via normal routing between different devices... VRFs provide a further level of traffic separation where we can build up different different LAN topologies inside each VRF totally independednt of each other and again the diameter of that VRF domain will depend upon how big the particualr traffic network is and the way its logically configured...
Generally MPLS VPN service is used for connecting different VRF Traffic for big networks and VRF-Lite solution is used on a single-CE to segregate muliple traffic types..Please make a note that Inter-VRF routing is not possible under normal VRF Instances without advanced features being enabled..So whenever we are planning for the VRFs we should factor in the network topology which will help us to decide the need for extending the VRF boundary and also any Inter-VRF routing as required.
Hope this helps to answer your question...
Regards
Varma
