If you are more familiar with Cisco kit, you then probably heard of VRFs and its little “brother” VRF-Lite (non-MPLS/MPBGP version). JunOS provides this feature too by means of Routing Instances; this feature, in JunOS, is called virtual-router. 

But virtual-router is just one type of routing instances; there is more:

  • virtual-router :: this is the closest version of Cisco’s VRF-Lite; it provides the ability to create additional, completely separate routing domains and routing tables. This effectively simulates multiple routers, in one – hence each virtual-router instance has its own set of routing tables  (inet.0, inet6.0, inet3.0, etc.)
  • forwarding :: routing instance used in FBF (Filter Based Forwarding) applications
  • no-forwarding :: this routing instance allows for separation of large networks into smaller administrative domains. In practice, unlike virtual-router instances, routing is still maintained within the master routing instance – the master routing instance. You would use this routing instance in scenarios where multiple routing processes (for example, multiple ospf routing instances)
  • l2vpn :: you would use this routing instance type in P2P L2 VPN o/ MPLS applications. If I am not mistaken, I believe Cisco calls this pseudo-wire
  • vpls :: this routing instance is also used in L2 VPN applications. The difference from the l2vpn routing instance is that a vpls emulates P2MP connections o/ MPLS – very useful indeed for wide area LANs (Layer 2 domain extensions)
  • vrf :: used in L3 VPN o/ MPLS implementations

In this blog, I’m going to illustrate one of the many applications of the virtual-router routing instance.


Thank you,
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