Here is a good definition about it. Got from one of the google searches. :)
Virtual Routing and Forwarding
Virtual routing and forwarding (VRF) is a technology included in IP(Internet Protocol) network routers that allows multiple instances of a routing table to exist in a router and work simultaneously. This increases functionality by allowing network paths to be segmented without using multiple devices.
Because traffic is automatically segregated, VRF also increases network security and can eliminate the need for encryption and authentication. Internet service providers
(ISPs) often take advantage of VRF to create separate virtual private networks (VPNs) for customers; thus the technology is also referred to as VPN routing and forwarding.
VRF acts like a logical router, but while a logical router may include many routing tables, a VRF instance uses only a single routing table. In addition, VRF requires a forwarding table that designates the next
hop for each data packet, a list of devices that may be called upon to forward the packet, and a set of rules and routing protocols that
govern how the packet is forwarded. These tables prevent traffic from being forwarded outside a specific VRF path and also keep out traffic that should remain outside the VRF path.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...