Vrf-Lite Configuration Guidelines - Cisco 4500M Software Manual

VRF-lite Configuration Guidelines

VRF-lite Configuration Guidelines
Consider these points when configuring VRF in your network:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Software Configuration Guide—Release 12.2(25)EW
28-4
A switch with VRF-lite is shared by multiple customers, and all customers have their own routing
tables.
Because customers use different VRF tables, the same IP addresses can be reused. Overlapped IP
addresses are allowed in different VPNs.
VRF-lite lets multiple customers share the same physical link between the PE and the CE. Trunk
ports with multiple VLANs separate packets among customers. All customers have their own
VLANs.
VRF-lite does not support all MPLS-VRF functionality: label exchange, LDP adjacency, or labeled
packets.
For the PE router, there is no difference between using VRF-lite or using multiple CEs. In
Figure 28-1, multiple virtual Layer 3 interfaces are connected to the VRF-lite device.
The Catalyst 4500 series switch supports configuring VRF by using physical ports, VLAN SVIs, or
a combination of both. The SVIs can be connected through an access port or a trunk port.
A customer can use multiple VLANs as long as they do not overlap with those of other customers.
A customer's VLANs are mapped to a specific routing table ID that is used to identify the
appropriate routing tables stored on the switch.
The Layer 3 TCAM resource is shared between all VRFs. To ensure that any one VRF has sufficient
CAM space, use the maximum routes command.
A Catalyst 4500 series switch using VRF can support one global network and up to 64 VRFs. The
total number of routes supported is limited by the size of the TCAM.
Most routing protocols (BGP, OSPF, EIGRP, RIP and static routing) can be used between the CE
and the PE. However, we recommend using external BGP (EBGP) for these reasons:
BGP does not require multiple algorithms to communicate with multiple CEs.
–
BGP is designed for passing routing information between systems run by different
–
administrations.
BGP makes it easy to pass attributes of the routes to the CE.
–
VRF-lite does not support IGRP and ISIS.
VRF-lite does not affect the packet switching rate.
Multicast cannot be configured on the same Layer 3 interface at the same time.
The capability vrf-lite subcommand under router ospf should be used when configuring OSPF as
the routing protocol between the PE and the CE.
Chapter 28 Configuring VRF-lite
OL-6696-01