Figure 28: Virtual Routers
VRs and VRFs are tools for implementing VPNs.
Routing Protocols
Your router implements the VRs by maintaining a separate instance of each data
structure for each VR and allowing each protocol (for example, TCP/UDP, RIP, OSPF,
and IS-IS) to be enabled on a case-by-case basis. A table of router interfaces associates
user connections (for example, PPP or ATM) with one or more IP interfaces within
a VR.
VPNs and VRFs
Your router supports VPNs and VRFs. For information about VPNs and VRFs, see
JUNOSe BGP and MPLS Configuration Guide.
VPNs
A VPN is a set of sites attached to a common network, but whose data is handled
separately from that common network.
VPNs enable private IP traffic to travel over a public TCP/IP network by tunneling
that traffic between VPN member sites. Different levels of security are available
depending on the security of the tunnel used between sites.
Your router supports VPNs consisting of VRs or VRFs. See RFC 2547—BGP/MPLS
VPNs (March 1999).. Additionally, your router supports tunnels built from GRE, IPSec,
L2TP, MPLS, and tunnels built from layer 2 circuits, such as Frame Relay and ATM.
VRFs
A VRF is a virtual routing and forwarding instance that exists within the context of
a VR. The VRF provides forwarding information to your router. The system looks up
a packet’s destination in the VRF associated with the interface on which the packet
is received. In general, any application that can be enabled in a VR can be enabled
in a VRF. VRFs are generally associated with the VPN behavior described in RFC
4364—BGP/MPLS IP Virtual Private Networks (VPNs).
When a VRF receives an update message, it needs to know whether it should add
the route to its routing table. Similarly, when a VRF sends update messages, it needs
540 â– Overview
JUNOSe 11.1.x System Basics Configuration Guide
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