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.