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How To |
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Introduction
In IP-based networks, VRF stands for Virtual Routing and Forwarding. This technology allows
multiple routing domains to co-exist within the same device at the same time. As the routing
domains are independent, overlapping IP addresses can be used without causing conflict. In
large service provider networks, virtual routing and forwarding is used in conjunction with
MPLS - Multi Protocol Label Switching - to separate each customer’s traffic into its own wide
area VPN. VRF is also known as VPN Routing and Forwarding (when used with MPLS), and is
also known as Multi-VRF.
What is VRF-lite?
VRF-lite is VRF without the need to run MPLS in the network. VRF-lite is used for isolating
customer networks - it allows multiple secure customer routing domains to co-exist in one
physical device simultaneously, which remain completely isolated from each other.
VRF-lite also allows the re-use of IP addresses on the same physical device. An IP address
range in one VLAN used in one VRF domain can simultaneously be used in another VLAN in
a different VRF domain within the same device. While VRF-lite will segregate traffic from
different customers/clients, VRF-lite can also allow for route leakage between VRF domains
(inter-VRF communication), by using static inter-VRF routes and/or dynamic route leakage via
BGP and associated route maps. This provides filtered access from one VRF routing domain
to another where the IP address ranges do not overlap.
This How to Note begins with a description of VRF-lite’s key features and the generic
commands used to configure VRF-lite. There are a number of simple configuration examples
provided to illustrate its use with OSPF, RIP, and BGP routing protocols. This is followed with
a configuration breakdown of a complex inter-VRF scenario, which includes overlapping IP
addresses and a range of routing protocols. Dynamic inter-VRF communication between the
global VRF domain and a VRF instance is also explained. Finally, a short list of diagnostics
commands are provided to help troubleshoot VRF-related issues.
Configure VRF-lite