VRF instance

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A VRF instance describes a function implemented in the Cisco IOS and routing hardware from other manufacturers that enables virtual routers on a physical router. The abbreviation VRF stands for Virtual Routing and Forwarding .

VRF instances are managed in Layer 3 of the OSI model ; each instance can use dedicated routing processes and tables. It is possible that two or more VRFs use overlapping IP address space. VRF instances are often used in the VPN environment, e.g. B. MPLS -VPN, used to logically separate networks from each other. Router interfaces (“ Interfaces ”) can be individually assigned to the VRF.

The role of the VRF entity

The VRF instance plays the decisive role in the contextualisation. Using the VRF instance, routing information from different VPNs can be distinguished from one another. The VRF instances can be named as desired. For example with: 

ip vrf "name"

This means that the virtual router can be addressed under a name; now you just have to set how the incoming and outgoing routing information is to be handled. A separate routing table is created for each. 

! pro Instanz
route-target import xxxxx:xfortlaufend 
route-target export xxxxx:xfortlaufend

Features of a VRF instance

Creating a virtual router creates a completely new network, ie in VRF instance 1, 2, 3, ..., n the complete address space can be assigned each time and each outgoing interface of each instance can be assigned the same IP address although only the hosts of the same instance are visible to the connected hosts. Communication between entities is not possible without internal, explicit routing.

literature

  • Volker Jung, Hans-Jürgen Warnecke (Hrsg.): Handbook for telecommunications. Springer Verlag, Berlin / Heidelberg 1998, ISBN 978-3-642-97703-9 .
  • Kristof Obermann, Martin Horneffer: Data network technologies for Next Generation Networks. 1st edition, Vieweg + Teubner Verlag, Wiesbaden 2009, ISBN 978-3-8348-0449-5 .
  • Andreas Prauschke: Ethernet Network-to Network Interconnection (E-NNI) . 1st edition, IGEL Verlag GmbH, 2009, ISBN 978-3-86815-153-4 .

Web links