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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing
Configuring Multi-VRF CE
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 t he 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 32-5 shows a configuration using Cisco ME 3400 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.
Figure32-5 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 pol icy labe ls , w hich a re u sed t o dist ingu is h
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 VLA N ID of t he i ngres s por t
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
CE2PE1 PE2
Service
provider
CE1
CE = Customer-edge device
PE = Provider-edge device
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