Table Of Contents
Configuring Layer 3 Virtualization
Layer 3 Virtualization
Overview of Layer 3 Virtualization
VRF and Routing
VRF-Lite
VRF-Aware Services
Reachability
Filtering
Combining Reachability and Filtering
Licensing Requirements for VRFs
Guidelines and Limitations
Default Settings
Configuring VRFs
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
Verifying the VRF Configuration
Configuration Examples for VRF
Related Topics
Additional References
Related Documents
Standards
Feature History for VRF
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
•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 IPv6 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 11-1 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 11-1 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 supports route leaking (import and export) between VRFs in a VRF lite scenario. The following are guidelines for the VRF route-leak feature:
•Supports route-leak between any two non-default VRFs and route-leak from the default VRF to any other VRF.
•Route-leak to the default VRF is not allowed as it is a global VRF.
•The route-leak feature is implemented using export and import route-targets under the VRF context.
•Filtering a part of the route-leak is done by using route-maps with the match ip address command.
•By default, the maximum prefix that can be leaked is 1000 routes. This is configurable.
•The route-leak feature must have an Enterprise license and the BGP feature enabled.
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 servics can select a particular VRF to reach a remote server or to filter information based on the selected VRF:
•AAA—See the Cisco Nexus 6000 Series NX-OS Security Configuration Guide, Release 6.0, for more information.
•Call Home—See the Cisco Nexus 6000 Series NX-OS System Management Configuration Guide, Release 6.0, for more information.
•HSRP—See Chapter 14 "Configuring HSRP" for more information.
•HTTP—See the Cisco Nexus 6000 Series NX-OS Fundamentals Configuration Guide, Release 6.0, for more information.
•Licensing—See the Cisco NX-OS Licensing Guide for more information.
•NTP—See the Cisco Nexus 6000 Series NX-OS System Management Configuration Guide, Release 6.0, for more information.
•RADIUS—See the Cisco Nexus 6000 Series NX-OS Security Configuration Guide, Release 6.0, for more information.
•Ping and Traceroute —See the Cisco Nexus 6000 Series NX-OS Fundamentals Configuration Guide, Release 6.0, for more information.
•SSH—See the Cisco Nexus 6000 Series NX-OS Fundamentals Configuration Guide, Release 6.0, for more information.
•SNMP—See the Cisco Nexus 6000 Series NX-OS System Management Configuration Guide, Release 6.0, for more information.
•Syslog—See the Cisco Nexus 6000 Series NX-OS System Management Configuration Guide, Release 6.0, for more information.
•TACACS+—See the Cisco Nexus 6000 Series NX-OS Security Configuration Guide, Release 6.0, for more information.
•TFTP—See the Cisco Nexus 6000 Series NX-OS Fundamentals Configuration Guide, Release 6.0, for more information.
•VRRP—See Chapter 15 "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 11-2 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 11-2 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 11-3 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 11-3 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 11-4 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 11-4 Service VRF Reachability Filtering
Licensing Requirements for VRFs
The following table shows the licensing requirements for this feature:
Product
|
License Requirement
|
Cisco NX-OS
|
VRFs require no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.
Note The NX-OS base license allows you to use the default VRF and you can use the management VRF for the mgmt0 port. The two default VRFs are automatically created. VRF-lite allows you to create additional VRFs. The additional VRFs require the Layer 3 LAN-Enterprise license.
|
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.
•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, static routing, EIGRP, EIGRPv6, OSPF, and OSPFv3.
•VRF-lite does not affect the packet switching rate.
Default Settings
Table 11-1 lists the default settings for VRF parameters.
Table 11-1 Default VRF Parameters
Parameters
|
Default
|
Configured VRFs
|
default, management
|
routing context
|
default VRF
|
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
| |
Command
|
Purpose
|
Step 1
|
configure terminal
Example:
switch# configure terminal
switch(config)#
|
Enters configuration mode.
|
Step 2
|
vrf context name
Example:
switch(config)# vrf context Enterprise
switch(config-vrf)#
|
Creates a new VRF and enters VRF configuration mode. The name can be any case-sensitive, alphanumeric string up to 32 characters.
|
Step 3
|
ip route {ip-prefix | ip-addr ip-mask}
{[next-hop | nh-prefix] | [interface
next-hop | nh-prefix]} [tag tag-value
[pref]
Example:
switch(config-vrf)# ip route 192.0.2.0/8
ethernet 1/2 192.0.2.4
|
Configures a static route and the interface for this static route. You can optionally configure the next-hop address. The preference value sets the administrative distance. The range is from 1 to 255. The default is 1.
|
Step 4
|
show vrf [vrf-name]
Example:
switch(config-vrf)# show vrf Enterprise
|
(Optional) Displays VRF information.
|
Step 5
|
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
|
(Optional) Saves this configuration change.
|
Use the no vrf context command to delete the VRF and the associated configuration:
Command
|
Purpose
|
no vrf context name
Example:
switch(config)# no vrf context Enterprise
|
Deletes the VRF and all 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)# 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. no switchport
4. vrf member vrf-name
5. ip-address ip-prefix/length
6. (Optional) show vrf vrf-name interface interface-type number
7. (Optional) copy running-config startup-config
DETAILED STEPS
| |
Command
|
Purpose
|
Step 1
|
configure terminal
Example:
switch# configure terminal
switch(config)#
|
Enters configuration mode.
|
Step 2
|
interface interface-type slot/port
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
|
Enters interface configuration mode.
Note If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.
Note
|
Step 3
|
no switchport
Example:
switch(config-if)# no switchport
|
Configures the interface as a Layer 3 routed interface.
|
Step 4
|
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
|
Adds this interface to a VRF.
|
Step 5
|
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
|
Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.
|
Step 6
|
show vrf vrf-name interface
interface-type number
Example:
switch(config-vrf)# show vrf Enterprise
interface ethernet 1/2
|
(Optional) Displays VRF information.
|
Step 7
|
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
|
(Optional) Saves this configuration change.
|
This example shows how to add an interface to the VRF:
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# no switchport
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. no switchport
7. vrf member vrf-name
8. ip address ip-prefix/length
9. ip router ospf instance-tag area area-id
10. (Optional) copy running-config startup-config
DETAILED STEPS
| |
Command
|
Purpose
|
Step 1
|
configure terminal
Example:
switch# configure terminal
switch(config)#
|
Enters configuration mode.
|
Step 2
|
router ospf instance-tag
Example:
switch(config-vrf)# router ospf 201
switch(config-router)#
|
Creates a new OSPFv2 instance with the configured instance tag.
|
Step 3
|
vrf vrf-name
Example:
switch(config-router)# vrf
RemoteOfficeVRF
switch(config-router-vrf)#
|
Enters VRF configuration mode.
|
Step 4
|
maximum-paths paths
Example:
switch(config-router-vrf)# maximum-paths
4
|
(Optional) Configures the maximum number of equal OSPFv2 paths to a destination in the route table for this VRF. Used for load balancing.
|
Step 5
|
interface interface-type slot/port
Example:
switch(config)# interface ethernet 1/2
switch(config-if)#
|
Enters interface configuration mode.
Note If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.
Note
|
Step 6
|
no switchport
Example:
switch(config-if)# no switchport
|
Configures the interface as a Layer 3 routed interface.
|
Step 7
|
vrf member vrf-name
Example:
switch(config-if)# vrf member
RemoteOfficeVRF
|
Adds this interface to a VRF.
|
Step 8
|
ip address ip-prefix/length
Example:
switch(config-if)# ip address
192.0.2.1/16
|
Configures an IP address for this interface. You must do this step after you assign this interface to a VRF.
|
Step 9
|
ip router ospf instance-tag area area-id
Example:
switch(config-if)# ip router ospf 201
area 0
|
Assigns this interface to the OSPFv2 instance and area configured.
|
Step 10
|
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
|
(Optional) Saves this configuration change.
|
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)# 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)# no switchport
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)# 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
| |
Command
|
Purpose
|
Step 1
|
configure terminal
Example:
switch# configure terminal
switch(config)#
|
Enters configuration mode.
|
Step 2
|
snmp-server host ip-address [filter-vrf
vrf-name] [use-vrf vrf-name]
Example:
switch(config)# snmp-server host
192.0.2.1 use-vrf Red
switch(config-vrf)#
|
Configures a global SNMP server and configures the VRF that Cisco NX-OS uses to reach the service. Use the filter-vrf keyword to filter information from the selected VRF to this server.
|
Step 3
|
vrf context vrf-name
Example:
switch(config)# vrf context Blue
switch(config-vrf)#
|
Creates a new VRF.
|
Step 4
|
ip domain-list domain-name
[all-vrfs][use-vrf vrf-name]
Example:
switch(config-vrf)# ip domain-list List
all-vrfs use-vrf Blue
switch(config-vrf)#
|
Configures the domain list in the VRF and optionally configures the VRF that Cisco NX-OS uses to reach the domain name listed.
|
Step 5
|
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
|
(Optional) Saves this configuration change.
|
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:
Command
|
Purpose
|
routing-context vrf vrf-name
Example:
switch# routing-context vrf red
switch%red#
|
Sets the routing context for all EXEC commands. Default routing context is the default VRF.
|
To return to the default VRF scope, use the following command in EXEC mode:
Command
|
Purpose
|
routing-context vrf default
Example:
switch%red# routing-context vrf default
switch#
|
Sets the default routing context.
|
Verifying the VRF Configuration
To display the VRF configuration information, perform one of the following tasks:
Command
|
Purpose
|
show vrf [vrf-name]
|
Displays the information for all or one VRF.
|
show vrf [vrf-name] detail
|
Displays detailed information for all or one VRF.
|
show vrf [vrf-name] [interface interface-type slot/port]
|
Displays the VRF status for an interface.
Note If this is a 10G breakout port, the slot/port syntax is slot/QSFP-module/port.
Note
|
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:
vrf context Red
snmp-server host 192.0.2.12 use-vrf Red
router ospf 201
interface ethernet 1/2
no switchport
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.:
!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
no switchport
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
no switchport
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 Nexus 6000 Series NX-OS Fundamentals Configuration Guide, Release 6.0
•Cisco Nexus 6000 Series NX-OS System Management Configuration Guide, Release 6.0
Additional References
For additional information related to implementing virtualization, see the following sections:
•Related Documents
•Standards
Related Documents
Related Topic
|
Document Title
|
VRF CLI
|
Cisco Nexus 5000 Series Command Reference, Cisco NX-OS Releases 4.x, 5.x
|
Standards
Standards
|
Title
|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
|
—
|
Feature History for VRF
Table 11-2 lists the release history for this feature.
Table 11-2 Feature History for VRF
Feature Name
|
Releases
|
Feature Information
|
VRF
|
6.0(2)N1(1)
|
This feature was introduced.
|
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