Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, Release 5.0(3)U1(1)

Configuring Layer 3 Virtualization

This chapter describes how to configure Layer 3 virtualization.

This chapter includes the following sections:

•Layer 3 Virtualization

•Licensing Requirements for VRFs

•Prerequisites for VRF, page 10-6

•Guidelines and Limitations

•Default Settings

•Configuring VRFs

•Verifying the VRF Configuration

•Configuration Examples for VRF

•Related Topics

•Additional References

•Feature History for VRF

Layer 3 Virtualization

This section includes the following topics:

•Overview of Layer 3 Virtualization

•VRF and Routing

•VRF-Aware Services

Overview of Layer 3 Virtualization

Cisco NX-OS supports virtual routing and forwarding instances (VRFs). Each VRF contains a separate address space with unicast and multicast route tables for IPv4 and makes routing decisions independent of any other VRF.

Each router has a default VRF and a management VRF. All Layer 3 interfaces and routing protocols exist in the default VRF until you assign them to another VRF. The mgmt0 interface exists in the management VRF.With the VRF-lite feature, the switch supports multiple VRFs in customer edge (CE) switches. VRF-lite allows a service provider to support two or more Virtual Private Networks (VPNs) with overlapping IP addresses using one interface.

Note The switch does not use Multiprotocol Label Switching (MPLS) to support VPNs.

VRF and Routing

All unicast and multicast routing protocols support VRFs. When you configure a routing protocol in a VRF, you set routing parameters for the VRF that are independent of routing parameters in another VRF for the same routing protocol instance.

You can assign interfaces and route protocols to a VRF to create virtual Layer 3 networks. An interface exists in only one VRF. Figure 9-1 shows one physical network split into two virtual networks with two VRFs. Routers Z, A, and B exist in VRF Red and form one address domain. These routers share route updates that do not include router C because router C is configured in a different VRF.

Figure 9-1 VRFs in a Network

By default, Cisco NX-OS uses the VRF of the incoming interface to select which routing table to use for a route lookup. You can configure a route policy to modify this behavior and set the VRF that Cisco NX-OS uses for incoming packets.

Cisco NX-OS prevents route leakage(import or export) between VRFs.

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 Multiprotocol Label Switching (MPLS) and MPLS control plane are not supported in the VRF-lite implementation.

Note VRF-lite interfaces must be Layer 3 interfaces.

VRF-Aware Services

A fundamental feature of the Cisco NX-OS architecture is that every IP-based feature is VRF aware.

The following VRF-aware services can select a particular VRF to reach a remote server or to filter information based on the selected VRF:

•AAA—See the Cisco Nexus 3000 Series NX-OS Security Configuration Guide, for more information.

•Call Home—See the Cisco Nexus 3000 Series NX-OS System Management Configuration Guide, for more information.

•HSRP—See Chapter 12, "Configuring HSRP" for more information.

•HTTP—See the Cisco NX-OS Fundamentals Configuration Guide,, for more information.

•Licensing—See theCisco NX-OS Licensing Guide for more information.

•NTP—See the Cisco Nexus 3000 Series NX-OS System Management Configuration Guide, for more information.

•RADIUS—See the Cisco Nexus 3000 Series NX-OS Security Configuration Guide, for more information.

•Ping and Traceroute —See the Cisco NX-OS Fundamentals Configuration Guide,, for more information.

•SSH—See the Cisco NX-OS Fundamentals Configuration Guide,, for more information.

•SNMP—See the Cisco Nexus 3000 Series NX-OS System Management Configuration Guide, for more information.

•Syslog—See the Cisco Nexus 3000 Series NX-OS System Management Configuration Guide, for more information.

•TACACS+—See the Cisco Nexus 3000 Series NX-OS Security Configuration Guide, for more information.

•TFTP—See the Cisco NX-OS Fundamentals Configuration Guide,, for more information.

•VRRP—See Chapter 13, "Configuring VRRP" for more information.

See the appropriate configuration guide for each service for more information on configuring VRF support in that service.

This section contains the following topics:

•Reachability

•Filtering

•Combining Reachability and Filtering

Reachability

Reachability indicates which VRF contains the routing information necessary to get to the server providing the service. For example, you can configure an SNMP server that is reachable on the management VRF. When you configure that server address on the router, you also configure which VRF that Cisco NX-OS must use to reach the server.

Figure 9-2 shows an SNMP server that is reachable over the management VRF. You configure router A to use the management VRF for SNMP server host 192.0.2.1.

Figure 9-2 Service VRF Reachability

Filtering

Filtering allows you to limit the type of information that goes to a VRF-aware service based on the VRF. For example, you can configure a syslog server to support a particular VRF. Figure 9-3 shows two syslog servers with each server supporting one VRF. syslog server A is configured in VRF Red, so Cisco NX-OS sends only system messages generated in VRF Red to syslog server A.

Figure 9-3 Service VRF Filtering

Combining Reachability and Filtering

You can combine reachability and filtering for VRF-aware services. You configure the VRF that Cisco NX-OS uses to connect to that service as well as the VRF that the service supports. If you configure a service in the default VRF, you can optionally configure the service to support all VRFs.

Figure 9-4 shows an SNMP server that is reachable on the management VRF. You can configure the SNMP server to support only the SNMP notifications from VRF Red, for example.

Figure 9-4 Service VRF Reachability Filtering

Licensing Requirements for VRFs

The following table shows the licensing requirements for this feature:

Guidelines and Limitations

VRFs have the following configuration guidelines and limitations:

•When you make an interface a member of an existing VRF, Cisco NX-OS removes all Layer 3 configuration. You should configure all Layer 3 parameters after adding an interface to a VRF.

•You should add the mgmt0 interface to the management VRF and configure the mgmt0 IP address and other parameters after you add it to the management VRF.

•If you configure an interface for a VRF before the VRF exists, the interface is operationally down until you create the VRF.

•Cisco NX-OS creates the default and management VRFs by default. You should make the mgmt0 interface a member of the management VRF.

•The write erase boot command does not remove the management VRF configuration. You must use the write erase command and then the write erase boot command.

VRF-lite has the following guidelines and limitations:

•A switch with VRF-lite has a separate IP routing table for each VRF, which is separate from the global routing table.

•Because VRF-lite uses different VRF tables, the same IP addresses can be reused. Overlapped IP addresses are allowed in different VPNs.

•VRF-lite does not support all MPLS-VRF functionality; it does not support label exchange, LDP adjacency, or labeled packets.

•Multiple virtual Layer 3 interfaces can be connected to a VRF-lite switch.

•The switch supports configuring a 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.

•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 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.

•VRF-lite supports BGP, RIP, and static routing.

•VRF-lite does not support EIGRP.

•VRF-lite does not affect the packet switching rate.

•Multicast cannot be configured on the same Layer 3 interface at the same time.

•VRF-lite is supported only on an IPv4 network.

Default Settings

Table 9-1 lists the default settings for VRF parameters.

Configuring VRFs

This section contains the following topics:

•Creating a VRF

•Assigning VRF Membership to an Interface

•Configuring VRF Parameters for a Routing Protocol

•Configuring a VRF-Aware Service

•Setting the VRF Scope

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Creating a VRF

You can create a VRF in a switch.

SUMMARY STEPS

1. configure terminal

2. vrf context name

3. ip route {ip-prefix | ip-addr ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [tag tag-value [pref]

4. (Optional) show vrf [vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

Use the no vrf context command to delete the VRF and the associated configuration:

Any commands available in global configuration mode are also available in VRF configuration mode.

This example shows how to create a VRF and add a static route to the VRF:

switch# configure terminal

switch(config)# vrf context Enterprise

switch(config-vrf)# ip route 192.0.2.0/8 ethernet 1/2

switch(config-vrf)# exit

switch(config)# copy running-config startup-config

Assigning VRF Membership to an Interface

You can make an interface a member of a VRF.

BEFORE YOU BEGIN

Assign the IP address for an interface after you have configured the interface for a VRF.

SUMMARY STEPS

1. configure terminal

2. interface interface-type slot/port

3. vrf member vrf-name

4. ip-address ip-prefix/length

5. (Optional) show vrf vrf-name interface interface-type number

6. (Optional) copy running-config startup-config

DETAILED STEPS

This example shows how to add an interface to the VRF:

switch# configure terminal

switch(config)# interface ethernet 1/2

switch(config-if)# vrf member RemoteOfficeVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# copy running-config startup-config

Configuring VRF Parameters for a Routing Protocol

You can associate a routing protocol with one or more VRFs. See the appropriate chapter for information on how to configure VRFs for the routing protocol. This section uses OSPFv2 as an example protocol for the detailed configuration steps.

SUMMARY STEPS

1. configure terminal

2. router ospf instance-tag

3. vrf vrf-name

4. (Optional) maximum-paths paths

5. interface interface-type slot/port

6. vrf member vrf-name

7. ip address ip-prefix/length

8. ip router ospf instance-tag area area-id

9. (Optional) copy running-config startup-config

DETAILED STEPS

This example shows how to create a VRF and add an interface to the VRF:

switch# configure terminal

switch(config)# vrf context RemoteOfficeVRF

switch(config-vrf)# exit

switch(config)# router ospf 201

switch(config-router)# vrf RemoteOfficeVRF

switch(config-router-vrf)# maximum-paths 4

switch(config-router-vrf)# interface ethernet 1/2

switch(config-if)# vrf member RemoteOfficeVRF

switch(config-if)# ip address 192.0.2.1/16

switch(config-if)# ip router ospf 201 area 0

switch(config-if)# exit

switch(config)# copy running-config startup-config

Configuring a VRF-Aware Service

You can configure a VRF-aware service for reachability and filtering. See the "VRF-Aware Services" section for links to the appropriate chapter or configuration guide for information on how to configure the service for VRFs. This section uses SNMP and IP domain lists as example services for the detailed configuration steps.

SUMMARY STEPS

1. configure terminal

2. snmp-server host ip-address [filter_vrf vrf-name] [use-vrf vrf-name]

3. vrf context [vrf-name]

4. ip domain-list domain-name [all-vrfs][use-vrf vrf-name]

5. (Optional) copy running-config startup-config

DETAILED STEPS

This example shows how to send SNMP information for all VRFs to SNMP host 192.0.2.1, reachable on VRF Red:

switch# configure terminal

switch(config)# snmp-server host 192.0.2.1 for-all-vrfs use-vrf Red

switch(config)# copy running-config startup-config

This example shows how to Filter SNMP information for VRF Blue to SNMP host 192.0.2.12, reachable on VRF Red:

switch# configure terminal

switch(config)# vrf definition Blue

switch(config-vrf)# snmp-server host 192.0.2.12 use-vrf Red

switch(config)# copy running-config startup-config

Setting the VRF Scope

You can set the VRF scope for all EXEC commands (for example, show commands). This automatically restricts the scope of the output of EXEC commands to the configured VRF. You can override this scope by using the VRF keywords available for some EXEC commands.

To set the VRF scope, use the following command in EXEC mode:

To return to the default VRF scope, use the following command in EXEC mode:

Verifying the VRF Configuration

To display the VRF configuration information, perform one of the following tasks:

Configuration Examples for VRF

This example shows how to configure VRF Red, add an SNMP server to that VRF, and add an instance of OSPF to VRF Red:

configure terminal

vrf context Red

 snmp-server host 192.0.2.12 use-vrf Red

router ospf 201

interface ethernet 1/2

 vrf member Red

 ip address 192.0.2.1/16

 ip router ospf 201 area 0

This example shows how to configure VRF Red and Blue, add an instance of OSPF to each VRF, and create an SNMP context for each OSPF instance in each VRF.:

configure terminal

!Create the VRFs

vrf context Red

vrf context Blue

!Create the OSPF instances and associate them with each VRF

feature ospf

router ospf Lab

 vrf Red

router ospf Production

 vrf Blue

!Configure one interface to use ospf Lab on VRF Red

interface ethernet 1/2

 vrf member Red

 ip address 192.0.2.1/16

 ip router ospf Lab area 0

 no shutdown

!Configure another interface to use ospf Production on VRF Blue

interface ethernet 10/2

 vrf member Blue

 ip address 192.0.2.1/16

 ip router ospf Production area 0

 no shutdown

!configure the SNMP server

snmp-server user admin network-admin auth md5 nbv-12345

snmp-server community public ro

!Create the SNMP contexts for each VRF

snmp-server context lab instance Lab vrf Red

snmp-server context production instance Production vrf Blue

Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF Red in 
this example.

Related Topics

The following topics can give more information on VRFs:

•Cisco NX-OS Fundamentals Configuration Guide,

•Cisco Nexus 3000 Series NX-OS System Management Configuration Guide

Additional References

For additional information related to implementing virtualization, see the following sections:

•Related Documents

•Standards

Related Documents

Standards

Feature History for VRF

Table 9-2 lists the release history for this feature.