VRF

VRF Introduction

 

The VRF stands for Virtual Routing and Forwarding is a technology for IP network routers that allows multiple routing table instances to coexist and run simultaneously in a single virtual router.

 

This feature allows network paths to be separated on the same device.  This cuts down on the number of devices needed and makes connections more efficient. It also makes networks more secure by automatically separating traffic.

 

Internet service providers often utilize VRF to create separate virtual private networks (VPNs) for their customers in a manner known as VPN routing and forwarding.

 

 

How to Configure a VRF?

 

A VRF is similar to a logical router, but with the difference that while a logical router may contain multiple routing tables, a VRF instance uses only one VRF table.

 

In addition, a VRF relies on a forwarding table, which is responsible for indicating the next-hop address of a packet, listing the devices that can participate in the forwarding of the packet, and establishing a set of guidelines and routing protocols that dictate the path a packet takes through the network.

 

Through these tables, the VRF ensures that traffic is transmitted only within the specified VRF path, preventing unauthorized traffic from entering or leaving that path.

What are The Application Scenarios for VRF?

 

VRF (Virtual Routing and Forwarding) runs at Layer 3 of the OSI model. It allows users to use overlapping or identical IP addresses without conflicts through independent routing instances. Users can segment their network paths without relying on multiple routers, improving network functionality.

 

Without VRF, customer traffic is routed through physical interfaces or subinterfaces and segregated by access control lists. As a result, VRFs are becoming more prevalent in enterprise LANs, data centers, and service provider environments using Multiprotocol Label Switching (MPLS) and Multiprotocol Border Gateway Protocol (MP-BGP).

 

The Advantages of VRF

 

It can virtually generate multiple independent routing instances on the same physical device.

 

Users can manage different routing tables at the same time to flexibly respond to diverse network requirements.

 

This feature is especially suitable for deployment scenarios of Multiprotocol Border Gateway Protocol (MP-BGP) and Multiprotocol Label Switching (MPLS).

 

The VPNs of multiple customers will not conflict even if they use the same IP address, thus guaranteeing network isolation.

 

Without the need for multiple physical routers, users can segment different network paths and optimize overall network performance.

Important Terms for Virtual Routing and Forwarding

 

When discussing Virtual Routing and Forwarding (VRF), there are several core terms that need to be clarified and some comparisons that need to be made to answer common questions. Below are explanations of the relevant terms:

 

VRF vs. VPN

VPN network provides private services to users over a public infrastructure. Typically, a VPN is a collection of sites for encrypted or unencrypted communications over the Internet via a public or other private network. It is important to note that the word “private” in VPN does not mean that the communication is encrypted or secure, it only means that the network path is isolated.

 

Virtual Routing and Forwarding (VRF) configurations allow multiple VPN environments to run simultaneously on the same physical network or router. With VRF, organizations can run isolated network services, such as wireless networking, voice (VoIP), data transmission, and video transmission, on a shared physical infrastructure without any impact on each other. VRF is also commonly used in Multiprotocol Label Switching (MPLS) architectures.

 

VDC vs. VRF vs. VLANs

VRF instances support the network virtualization capabilities of Layer 3 of the OSI model. Virtual Device Context (VDC) on the other hand focuses on the virtualization of the device itself. a VDC can virtualize a physical switch into multiple independent devices. each of which can have its own VRF and VLAN configurations.

 

Virtual Local Area Networks (VLANs), on the other hand, operate at Layer 2 of the OSI model and divide Ethernet into multiple virtual networks to improve network security and performance without affecting the physical topology of the network. In contrast, VRFs can create multiple virtual networks within the same physical hardware, but act at a higher level, operating at Layer 3.

 

Static Routing

Each VPN routing and forwarding instance (either default or user-defined) will have a corresponding static route configuration. Instead of a specific VRF, users can configure static routes for the default VRF so that in VRF mode, users have the flexibility to customize static routes to meet specific needs.