Cisco Catalyst 3750 Software Configuration Manual page 679

Chapter 28 Configuring IP Unicast Routing
• 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 28-6
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 Catalyst 3750 Metro
switches. Because multi-VRF CE is a Layer 3 feature, each interface in a VRF must be a Layer 3
interface.
Figure 28-6 Catalyst 3750 Metro 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 in multi-VRF-CE-related data structures and adds
the VLAN ID and policy label to the VLAN database.
When the 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.
78-15870-01
shows a configuration using Catalyst 3750 Metro switches as multiple virtual CEs. This
VPN 1
CE1
VPN 2
PE1 PE2
Service
provider
CE = Customer-edge device
PE = Provider-edge device
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring Multi-VRF CE
VPN 1
CE2
VPN 2
28-77