Virtual Routing & Forwarding and How Is it Configured?

Virtual Routing and Forwarding allows you to use multiple routing tables on one router. The practice can bring both security and efficiency benefits, allowing you to run multiple logical networks with entirely separate address spaces without having to purchase additional network equipment. VRF is often used by Internet Service Providers, as it allows them to provide multiple private networks to clients from one set of hardware.

 Routing Tables

  • A routing table is a list of IP addresses and their corresponding network locations. Routers maintain routing tables in order to ensure that network traffic is always forwarded on to the correct location. By examining a data packet’s end destination, the router can work out where it should send that data to on the next hop of its journey, even if it cannot send the data directly to that destination. Using tables allows routers to quickly adjust to changing network conditions, such as equipment outages and design changes.

Virtual Routing and Forwarding

  • Each network requires its own unique routing table, as trying to use multiple tables for the same network or multiple networks across the same table would likely result in IP address conflicts and dropped data. However, VRF allows routers to virtualize their routing tables. This means that the router software runs several different instances of its routing algorithm at once, effectively acting as multiple separate routers despite only comprising one physical hardware unit.

Security Benefits

  • The virtualized routing tables of a VRF router are entirely separate. Each network client has no knowledge of or interaction with address spaces other than the one maintained by the routing table it uses. This means that if two devices on different routing tables want to communicate, they have to do so as if they were on entirely separate networks. As such, VRF provides a security benefit by allowing users to segregate devices that should not be locally accessible from other machines without the need for encryption.

Cost Implications

  • VRF provides an efficient way of running several networks at once. For example, a service provider might use the technology to provide network infrastructure to multiple clients from the same physical router. However, VRF can increase the amount of traffic a router needs to send, as it means that the device is effectively doing several jobs at once. This could result in the service provider needing to invest in upgraded network equipment in order to meet bandwidth demands.
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