Understanding Multi-Vrf Ce - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Chapter 35 Configuring IP Unicast Routing

Understanding Multi-VRF CE

Multi-VRF CE is a feature that allows a service provider to support two or more VPNs, where IP
addresses can be overlapped among the VPNs. Multi-VRF CE uses input interfaces to distinguish routes
for different VPNs and forms virtual packet-forwarding tables by associating one or more Layer 3
interfaces with each VRF. Interfaces in a VRF can be either physical, such as Ethernet ports, or logical,
such as VLAN SVIs, but an interface cannot belong to more than one VRF at any time.
Note Multi-VRF CE interfaces must be Layer 3 interfaces.
Multi-VRF CE includes these devices:
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With multi-VRF CE, multiple customers can share one CE, and only one physical link is used between
the CE and the PE. The shared CE maintains separate VRF tables for each customer and switches or
routes packets for each customer based on its own routing table. Multi-VRF CE extends limited PE
functionality to a CE device, giving it the ability to maintain separate VRF tables to extend the privacy
and security of a VPN to the branch office.
Figure 35-6
is suited for customers who have low bandwidth requirements for their VPN service, for example, small
companies. In this case, multi-VRF CE support is required in the Catalyst 3750 switches. Because
multi-VRF CE is a Layer 3 feature, each interface in a VRF must be a Layer 3 interface.
OL-8550-02
Customer edge (CE) devices provide customers access to the service-provider network over a data
link to one or more provider edge routers. The CE device advertises the site's local routes to the
router and learns the remote VPN routes from it. A Catalyst 3750 switch can be a CE.
Provider edge (PE) routers exchange routing information with CE devices by using static routing or
a routing protocol such as BGP, RIPv2, OSPF, or EIGRP. The PE is only required to maintain VPN
routes for those VPNs to which it is directly attached, eliminating the need for the PE to maintain
all of the service-provider VPN routes. Each PE router maintains a VRF for each of its directly
connected sites. Multiple interfaces on a PE router can be associated with a single VRF if all of these
sites participate in the same VPN. Each VPN is mapped to a specified VRF. After learning local
VPN routes from CEs, a PE router exchanges VPN routing information with other PE routers by
using internal BGP (IBPG).
Provider routers or core routers are any routers in the service provider network that do not attach to
CE devices.
shows a configuration using Catalyst 3750 switches as multiple virtual CEs. This scenario
Catalyst 3750 Switch Software Configuration Guide
Configuring Multi-VRF CE
35-65