Catalyst 4500 Series Switch Cisco IOS Software Configuration Guide, 12.2(18)EW
Configuring VRF-lite
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Configuring VRF-lite

Table Of Contents

Configuring VRF-lite

Understanding VRF-lite

Default VRF-lite Configuration

VRF-lite Configuration Guidelines

Configuring VRFs

Configuring a VPN Routing Session

Configuring BGP PE to CE Routing Sessions

VRF-lite Configuration Example

Configuring Switch S8

Configuring Switch S20

Configuring Switch S11

Configuring the PE Switch S3

Displaying VRF-lite Status


Configuring VRF-lite


Virtual Private Networks (VPNs) provide a secure way for customers to share bandwidth over an ISP backbone network. A VPN is a collection of sites sharing a common routing table. A customer site is connected to the service provider network by one or more interfaces, and the service provider associates each interface with a VPN routing table. A VPN routing table is called a VPN routing/forwarding (VRF) table.

With the VRF-lite feature, the Catalyst 4500 series switch supports multiple VPN routing/forwarding instances in customer edge devices. (VRF-lite is also termed multi-VRF CE, or multi-VRF Customer Edge Device). VRF-lite allows a service provider to support two or more VPNs with overlapping IP addresses using one interface.


Note The switch does not use Multiprotocol Label Switching (MPLS) to support VPNs. For information about MPLS VRF, refer to the Cisco IOS Switching Services Configuration Guide at:

http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/mp_vpn_ipv4_ipv6_ps6922_TSD_Products_Configuration_Guide_Chapter.html


This chapter includes these topics:

Understanding VRF-lite

Default VRF-lite Configuration

VRF-lite Configuration Guidelines

Configuring VRFs

Configuring a VPN Routing Session

Configuring BGP PE to CE Routing Sessions

VRF-lite Configuration Example

Displaying VRF-lite Status


Note For complete syntax and usage information for the switch commands used in this chapter, see the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/hw/switches/ps4324/index.html

If the command is not found in the Cisco Catalyst 4500 Command Reference, you can locate it in the larger Cisco IOS library. Refer to the Catalyst 4500 Series Switch Cisco IOS Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/ps6350/index.html


Understanding VRF-lite

VRF-lite is a feature that enables a service provider to support two or more VPNs, where IP addresses can be overlapped among the VPNs. VRF-lite uses input interfaces to distinguish routes for different VPNs and forms virtual packet-forwarding tables by associating one or more Layer 3 interfaces with each VRF. Interfaces in a VRF can be either physical, such as Ethernet ports, or logical, such as VLAN SVIs, but a Layer 3 interface cannot belong to more than one VRF at any time.


Note VRF-Lite support on Cat 4500 does not include the Provider Edge MPLS funcitonality. More specifically, MPLS label switching and MPLS control plane are not supported in the VRF-Lite implementation.



Note VRF-lite interfaces must be Layer 3 interfaces.


VRF-lite includes these devices:

Customer edge (CE) devices provide customer access to the service provider network over a data link to one or more provider edge routers. The CE device advertises the site's local routes to the provider edge router and learns the remote VPN routes from it. A Catalyst 4500 switch can be a CE.

Provider edge (PE) routers exchange routing information with CE devices by using static routing or a routing protocol such as BGP, RIPv1, or RIPv2.

The PE is only required to maintain VPN routes for those VPNs to which it is directly attached, eliminating the need for the PE to maintain all of the service provider VPN routes. Each PE router maintains a VRF for each of its directly connected sites. Multiple interfaces on a PE router can be associated with a single VRF if all of these sites participate in the same VPN. Each VPN is mapped to a specified VRF. After learning local VPN routes from CEs, a PE router exchanges VPN routing information with other PE routers by using internal BGP (IBPG).

Provider routers (or core routers) are any routers in the service provider network that do not attach to CE devices.

With VRF-lite, multiple customers can share one CE, and only one physical link is used between the CE and the PE. The shared CE maintains separate VRF tables for each customer and switches or routes packets for each customer based on its own routing table. VRF-lite extends limited PE functionality to a CE device, giving it the ability to maintain separate VRF tables to extend the privacy and security of a VPN to the branch office.

Figure 23-1 shows a configuration where each Catalyst 4500 switch acts as multiple virtual CEs. Because VRF-lite is a Layer 3 feature, each interface in a VRF must be a Layer 3 interface.

Figure 23-1 Catalyst 4500 Switches Acting as Multiple Virtual CEs

This is the packet-forwarding process in a VRF-lite CE-enabled network as shown in Figure 23-1:

When the CE receives a packet from a VPN, it looks up the routing table based on the input interface. When a route is found, the CE 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 the egress PE 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 interface to look up the correct VPN routing table. If a route is found, the CE forwards the packet within the VPN.

To configure VRF, 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 VRF-lite 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 VRF-lite Configuration

Table 23-1 shows the default VRF configuration.

Table 23-1 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

None.

Forwarding table

The default for an interface is the global routing table.


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 23-1, 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.

Configuring VRFs

To configure one or more VRFs, perform this task:

 
Command
Purpose

Step 1 

Switch# configure terminal

Enters global configuration mode.

Step 2 

Switch(config)# ip routing

Enables IP routing.

Step 3 

Switch(config)# ip vrf vrf-name

Names the VRF, and enter VRF configuration mode.

Step 4 

Switch(config-vrf)# rd 
route-distinguisher

Creates a VRF table by specifying a route distinguisher. Enter either an AS number and an arbitrary number (xxx:y) or an IP address and arbitrary number (A.B.C.D:y).

Step 5 

Switch(config-vrf)# route-target 
{export | import | both} 
route-target-ext-community

Creates a list of import, export, or import and export route target communities for the specified VRF. Enter either an AS system number and an arbitrary number (xxx:y) or an IP address and an arbitrary number (A.B.C.D:y).

Note This command is effective only if BGP is running.

Step 6 

Switch(config-vrf)# import map 
route-map

(Optional) Associates a route map with the VRF.

Step 7 

Switch(config-vrf)# interface 
interface-id

Enters interface configuration mode and specify the Layer 3 interface to be associated with the VRF. The interface can be a routed port or SVI.

Step 8 

Switch(config-if)# ip vrf forwarding 
vrf-name

Associates the VRF with the Layer 3 interface.

Step 9 

Switch(config-if)# end

Returns to privileged EXEC mode.

Step 10 

Switch# show ip vrf [brief | detail | 
interfaces] [vrf-name]

Verifies the configuration. Display information about the configured VRFs.

Step 11 

Switch# copy running-config 
startup-config

(Optional) Saves your entries in the configuration file.


Note For complete syntax and usage information for the commands, refer to the switch command reference for this release and the Cisco IOS Switching Services Command Reference for Release 12.2.


Use the no ip vrf vrf-name global configuration command to delete a VRF and to remove all interfaces from it. Use the no ip vrf forwarding interface configuration command to remove an interface from the VRF.

Configuring a VPN Routing Session

Routing within the VPN can be configured with any supported routing protocol (RIP, OSPF, or BGP) or with static routing. The configuration shown here is for OSPF, but the process is the same for other protocols.

To configure OSPF in the VPN, perform this task:

 
Command
Purpose

Step 1 

Switch# configure terminal

Enters global configuration mode.

Step 2 

Switch(config)# router ospf process-id vrf vrf-name

Enables OSPF routing, specifies a VPN forwarding table, and enters router configuration mode.

Step 3 

Switch(config-router)# log-adjacency-changes

(Optional) Logs changes in the adjacency state. This is the default state.

Step 4 

Switch(config-router)# redistribute bgp autonomous-system-number subnets

Sets the switch to redistribute information from the BGP network to the OSPF network.

Step 5 

Switch(config-router)# network network-number area area-id

Defines a network address and mask on which OSPF runs and the area ID for that network address.

Step 6 

Switch(config-router)# end

Returns to privileged EXEC mode.

Step 7 

Switch# show ip ospf process-id

Verifies the configuration of the OSPF network.

Step 8 

Switch# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Use the no router ospf process-id vrf vrf-name global configuration command to disassociate the VPN forwarding table from the OSPF routing process.

Configuring BGP PE to CE Routing Sessions

To configure a BGP PE to CE routing session, perform this task:

 
Command
Purpose

Step 1 

Switch# configure terminal

Enters global configuration mode.

Step 2 

Switch(config)# router bgp autonomous-system-number

Configures the BGP routing process with the AS number passed to other BGP routers and enters router configuration mode.

Step 3 

Switch(config-router)# network network-number mask network-mask

Specifies a network and mask to announce using BGP.

Step 4 

Switch(config-router)# redistribute ospf process-id match internal

Sets the switch to redistribute OSPF internal routes.

Step 5 

Switch(config-router)# network network-number area area-id

Defines a network address and mask on which OSPF runs and the area ID for that network address.

Step 6 

Switch(config-router-af)# address-family ipv4 vrf vrf-name

Defines BGP parameters for PE to CE routing sessions and enters VRF address-family mode.

Step 7 

Switch(config-router-af)# neighbor address remote-as as-number

Defines a BGP session between PE and CE routers.

Step 8 

Switch(config-router-af)# neighbor address activate

Activates the advertisement of the IPv4 address family.

Step 9 

Switch(config-router-af)# end

Returns to privileged EXEC mode.

Step 10 

Switch# show ip bgp [ipv4] [neighbors]

Verifies BGP configuration.

Step 11 

Switch# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Use the no router bgp autonomous-system-number global configuration command to delete the BGP routing process. Use the command with keywords to delete routing characteristics.

VRF-lite Configuration Example

Figure 23-2 is a simplified example of the physical connections in a network similar to that in Figure 23-1. OSPF is the protocol used in VPN1, VPN2, and the global network. BGP is used in the CE to PE connections. The example commands show how to configure the CE switch S8 and include the VRF configuration for switches S20 and S11 and the PE router commands related to traffic with switch S8. Commands for configuring the other switches are not included but would be similar.

Figure 23-2 VRF-lite Configuration Example

Configuring Switch S8

On switch S8, enable routing and configure VRF.

Switch# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)# ip routing 
Switch(config)# ip vrf v11
Switch(config-vrf)# rd 800:1
Switch(config-vrf)# route-target export 800:1
Switch(config-vrf)# route-target import 800:1
Switch(config-vrf)# exit
Switch(config)# ip vrf v12
Switch(config-vrf)# rd 800:2
Switch(config-vrf)# route-target export 800:2
Switch(config-vrf)# route-target import 800:2
Switch(config-vrf)# exit

Configure the loopback and physical interfaces on switch S8. Fast Ethernet interface 3/5 is a trunk connection to the PE. Interfaces 3/7 and 3/11 connect to VPNs:

Switch(config)# interface loopback1
Switch(config-if)# ip vrf forwarding v11
Switch(config-if)# ip address 8.8.1.8 255.255.255.0
Switch(config-if)# exit

Switch(config)# interface loopback2
Switch(config-if)# ip vrf forwarding v12
Switch(config-if)# ip address 8.8.2.8 255.255.255.0
Switch(config-if)# exit

Switch(config)# interface FastEthernet3/5
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk
Switch(config-if)# no ip address
Switch(config-if)# exit
Switch(config)# interface FastEthernet3/8
Switch(config-if)# switchport access vlan 208
Switch(config-if)# no ip address
Switch(config-if)# exit
Switch(config)# interface FastEthernet3/11
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk
Switch(config-if)# no ip address
Switch(config-if)# exit

Configure the VLANs used on switch S8. VLAN 10 is used by VRF 11 between the CE and the PE. VLAN 20 is used by VRF 12 between the CE and the PE. VLANs 118 and 208 are used for VRF for the VPNs that include switch S11 and switch S20, respectively:

Switch(config)# interface Vlan10
Switch(config-if)# ip vrf forwarding v11
Switch(config-if)# ip address 38.0.0.8 255.255.255.0
Switch(config-if)# exit
Switch(config)# interface Vlan20
Switch(config-if)# ip vrf forwarding v12
Switch(config-if)# ip address 38.0.0.8 255.255.255.0
Switch(config-if)# exit
Switch(config)# interface Vlan118
Switch(config-if)# ip vrf forwarding v12
Switch(config-if)# ip address 118.0.0.8 255.255.255.0
Switch(config-if)# exit
Switch(config)# interface Vlan208
Switch(config-if)# ip vrf forwarding v11
Switch(config-if)# ip address 208.0.0.8 255.255.255.0
Switch(config-if)# exit

Configure OSPF routing in VPN1 and VPN2:

Switch(config)# router ospf 1 vrf vl1
Switch(config-router)# redistribute bgp 800 subnets
Switch(config-router)# network 208.0.0.0 0.0.0.255 area 0
Switch(config-router)# exit 
Switch(config)# router ospf 2 vrf vl2
Switch(config-router)# redistribute bgp 800 subnets
Switch(config-router)# network 118.0.0.0 0.0.0.255 area 0
Switch(config-router)# exit 

Configure BGP for CE to PE routing:

Switch(config)# router bgp 800
Switch(config-router)# address-family ipv4 vrf vl2
Switch(config-router-af)# redistribute ospf 2 match internal
Switch(config-router-af)# neighbor 83.0.0.3 remote-as 100
Switch(config-router-af)# neighbor 83.0.0.3 activate
Switch(config-router-af)# network 8.8.2.0 mask 255.255.255.0
Switch(config-router-af)# exit 
Switch(config-router)# address-family ipv4 vrf vl1
Switch(config-router-af)# redistribute ospf 1 match internal
Switch(config-router-af)# neighbor 38.0.0.3 remote-as 100
Switch(config-router-af)# neighbor 38.0.0.3 activate
Switch(config-router-af)# network 8.8.1.0 mask 255.255.255.0
Switch(config-router-af)# end 

Configuring Switch S20

Configure S20 to connect to CE:

Switch# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)# ip routing 
Switch(config)# interface Fast Ethernet 0/7
Switch(config-if)# no switchport
Switch(config-if)# ip address 208.0.0.20 255.255.255.0
Switch(config-if)# exit

Switch(config)# router ospf 101
Switch(config-router)# network 208.0.0.0 0.0.0.255 area 0
Switch(config-router)# end 

Configuring Switch S11

Configure S11 to connect to CE:

Switch# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)# ip routing 
Switch(config)# interface Gigabit Ethernet 0/3
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk 
Switch(config-if)# no ip address
Switch(config-if)# exit

Switch(config)# interface Vlan118
Switch(config-if)# ip address 118.0.0.11 255.255.255.0
Switch(config-if)# exit

Switch(config)# router ospf 101
Switch(config-router)# network 118.0.0.0 0.0.0.255 area 0
Switch(config-router)# end 

Configuring the PE Switch S3

On switch S3 (the router), these commands configure only the connections to switch S8:

Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# ip vrf v1
Router(config-vrf)# rd 100:1
Router(config-vrf)# route-target export 100:1
Router(config-vrf)# route-target import 100:1
Router(config-vrf)# exit

Router(config)# ip vrf v2
Router(config-vrf)# rd 100:2
Router(config-vrf)# route-target export 100:2
Router(config-vrf)# route-target import 100:2
Router(config-vrf)# exit
Router(config)# ip cef
Router(config)# interface Loopback1
Router(config-if)# ip vrf forwarding v1
Router(config-if)# ip address 3.3.1.3 255.255.255.0
Router(config-if)# exit

Router(config)# interface Loopback2
Router(config-if)# ip vrf forwarding v2
Router(config-if)# ip address 3.3.2.3 255.255.255.0
Router(config-if)# exit

Router(config)# interface Fast Ethernet3/0.10
Router(config-if)# encapsulation dot1q 10
Router(config-if)# ip vrf forwarding v1
Router(config-if)# ip address 38.0.0.3 255.255.255.0
Router(config-if)# exit

Router(config)# interface Fast Ethernet3/0.20
Router(config-if)# encapsulation dot1q 20
Router(config-if)# ip vrf forwarding v2
Router(config-if)# ip address 83.0.0.3 255.255.255.0
Router(config-if)# exit

Router(config)# router bgp 100
Router(config-router)# address-family ipv4 vrf v2
Router(config-router-af)# neighbor 38.0.0.8 remote-as 800
Router(config-router-af)# neighbor 38.0.0.8 activate
Router(config-router-af)# network 3.3.2.0 mask 255.255.255.0
Router(config-router-af)# exit 
Router(config-router)# address-family ipv4 vrf vl
Router(config-router-af)# neighbor 38.0.0.8 remote-as 800
Router(config-router-af)# neighbor 38.0.0.8 activate
Router(config-router-af)# network 3.3.1.0 mask 255.255.255.0
Router(config-router-af)# end 

Displaying VRF-lite Status

To display information about VRF-lite configuration and status, perform one of the following tasks:

Command
Purpose

Switch# show ip protocols vrf vrf-name

Displays routing protocol information associated with a VRF.

Switch# show ip route vrf vrf-name [connected] [protocol [as-number]] [list] [mobile] [odr] [profile] [static] [summary] [supernets-only]

Displays IP routing table information associated with a VRF.

Switch# show ip vrf [brief | detail | interfaces] [vrf-name]

Displays information about the defined VRF instances.


For more information about the information in the displays, refer to the Cisco IOS Switching Services Command Reference for Release 12.2.