To Next Page

To Previous Page

28-4

Software Configuration Guide—Release 12.2(25)EW

OL-6696-01

Chapter 28 Configuring VRF-lite

VRF-lite Configuration Guidelines

Consider these points when configuring VRF in your network:

• 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.

Cisco 4500M User Manual

Other manuals for Cisco 4500M