Vrf-Lite Configuration Guidelines - Cisco Catalyst 4500 Series Configuration Manual

VRF-lite Configuration Guidelines

Table 39-1
Feature
VRF maximum routes
Forwarding table
VRF-lite Configuration Guidelines
Consider these points when configuring VRF in your network:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
39-4
Default VRF Configuration (continued)
Default Setting
None.
The default for an interface is the global routing table.
A switch with VRF-lite is shared by multiple customers, and all customers have their own routing
tables.
Because customers use different VRF tables, you can reuse the same IP addresses. 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 39-1, 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. You can connect SVIs through an access port or a trunk port.
A customer can use multiple VLANs as long because 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.
You can use most routing protocols (BGP, OSPF, EIGRP, RIP and static routing) 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.
Starting with Cisco IOS Release 12.2(50)SG, Multicast and VRF can be configured together on a
Layer 3 interface.
The Catalyst 4500 series switch supports all the PIM protocols (PIM-SM, PIM-DM, PIM-SSM, PIM
BiDIR).
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 39 Configuring VRF-lite
OL-25340-01