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Configuring IP Unicast Routing
Configuring Multi-VRF CE
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.
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
Feature
VRF
Maps
VRF maximum routes
Forwarding table
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.
Default Setting
Disabled. No VRFs are defined.
No import maps, export maps, or route maps are defined.
5000
The default for an interface is the global routing table.
896
- Quick Links:
- Configuration Overview
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