Active and programmable networks allow innovative new services to be deployed rapidly. However, in a carrier grade network, it is imperative to maintain a scalable fast path mechanism so that the delay and throughput requirements are met. This is particularly important since, in many cases, network-level processing is only needed for a subset of packets and the remainder of traffic must be forwarded on the fast path. It is a challenge to design a cost effective node architecture that can satisfy this requirement. Current models are often 'revolutionary' and may not scale to the required performance levels of a carrier grade network. We develop an evolutionary architecture that uses MPLS label stacks to enable efficient and scalable extraction of active packets from the fast path without penalising the rest of the traffic. Our model can be used to extend the reach of programmable networks over a legacy infrastructure and provide a migratory path for existing carriers towards a programmable infrastructure.