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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
This is the packet-forwarding process in a multi-VRF-CE-enabled network:
•
When the switch receives a packet from a VPN, the switch looks up the routing table based on the
input policy label number. When a route is found, the switch forwards the packet to the PE.
•
When the ingress PE receives a packet from the CE, it performs a VRF lookup. When a route is
found, the router adds a corresponding MPLS label to the packet and sends it to the MPLS network.
•
When an egress PE receives a packet from the network, it strips the label and uses the label to
identify the correct VPN routing table. Then it performs the normal route lookup. When a route is
found, it forwards the packet to the correct adjacency.
•
When a CE receives a packet from an egress PE, it uses the input policy label to look up the correct
VPN routing table. If a route is found, it forwards the packet within the VPN.
To configure VRF, you create a VRF table and specify the Layer 3 interface associated with the VRF.
Then configure the routing protocols in the VPN and between the CE and the PE. BGP is the preferred
routing protocol used to distribute VPN routing information across the provider’s backbone. The
multi-VRF CE network has three major components:
•
VPN route target communities—lists of all other members of a VPN community. You need to
configure VPN route targets for each VPN community member.
•
Multiprotocol BGP peering of VPN community PE routers—propagates VRF reachability
information to all members of a VPN community. You need to configure BGP peering in all PE
routers within a VPN community.
•
VPN forwarding—transports all traffic between all VPN community members across a VPN
service-provider network.
Default Multi-VRF CE Configuration
Table 29-14
shows the default VRF configuration.
Multi-VRF CE Configuration Guidelines
These are considerations when configuring VRF in your network:
•
A switch with multi-VRF CE is shared by multiple customers, and each customer has its own routing
table.
•
Because customers use different VRF tables, the same IP addresses can be reused. Overlapped IP
addresses are allowed in different VPNs.
•
Multi-VRF CE lets multiple customers share the same physical link between the PE and the CE.
Trunk ports with multiple VLANs separate packets among customers. Each customer has its own
VLAN.
Table 29-14
Default VRF Configuration
Feature
Default Setting
VRF
Disabled. No VRFs are defined.
Maps
No import maps, export maps, or route maps are defined.
VRF maximum routes
5000
Forwarding table
The default for an interface is the global routing table.
