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Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 29 Configuring IP Unicast Routing
Configuring Multi-VRF CE
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.
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 29-8
shows a configuration using Cisco ME switches as multiple virtual CEs. This scenario 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 Cisco ME switches. Because
multi-VRF CE is a Layer 3 feature, each interface in a VRF must be a Layer 3 interface.
Figure 29-8
Switches Acting as Multiple Virtual CEs
When the CE switch receives a command to add a Layer 3 interface to a VRF, it sets up the appropriate
mapping between the VLAN ID and the policy label (PL) in multi-VRF-CE-related data structures and
adds the VLAN ID and PL to the VLAN database.
When multi-VRF CE is configured, the Layer 3 forwarding table is conceptually partitioned into two
sections:
•
The multi-VRF CE routing section contains the routes from different VPNs.
•
The global routing section contains routes to non-VPN networks, such as the Internet.
VLAN IDs from different VRFs are mapped into different policy labels, which are used to distinguish
the VRFs during processing. If no route is found in the multi-VRF CE section of the Layer 3 forwarding
table, the global routing section is used to determine the forwarding path. For each new VPN route
learned, the Layer 3 setup function retrieves the policy label by using the VLAN ID of the ingress port
and inserts the policy label and new route to the multi-VRF CE routing section. If the packet is received
from a routed port, the port internal VLAN ID number is used; if the packet is received from an SVI, the
VLAN number is used.
VPN 1
VPN 2
VPN 1
VPN 2
CE2
PE1
PE2
Service
provider
CE1
CE = Customer-edge device
PE = Provider-edge device
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