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This chapter describes how to configure Layer 3 virtualization.
This chapter includes the following sections:
•Licensing Requirements for VRFs
This section contains the following topics:
•Overview of Layer 3 Virtualization
Cisco NX-OS further virtualizes each VDC to support virtual routing and forwarding instances (VRFs). You can configure multiple VRFs in a VDC. 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.
Figure 14-1 Multiple VRFs in VDCs
A VRF name is local to a VDC, so you can configure two VRFs with the same name if the VRFs exist in different VDCs. In Figure 14-1, VRF A in VDC 2 is independent of VRF B and VRF A in VDC n.
Each router has a management VRF and a default VRF:
Management VRF
• The management VRF is for management purposes only.
• Only the mgmt 0 interface can be in the management VRF.
• The mgmt 0 interface cannot be assigned to another VRF.
• The mgmt 0 interface is shared among multiple VDCs.
• No routing protocols can run in the management VRF (static only).
Default VRF
• All Layer 3 interfaces exist in the default VRF until they are assigned to another VRF.
• Routing protocols run in the default VRF context unless another VRF context is specified.
• The default VRF uses the default routing context for all show commands.
• The default VRF is similar to the global routing table concept in Cisco IOS.
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 14-2 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 14-2 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. See Chapter 17 "Configuring Policy-Based Routing" for more information.
Cisco NX-OS prevents route leakage(import or export) between VRFs.
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 7000 Series NX-OS Security Configuration Guide, Release 4.x for more information.
•Call Home—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for more information.
•DNS—See Chapter 4 "Configuring DNS" for more information.
•GLBP—See Chapter 18 "Configuring GLBP" for more information.
•HSRP—See Chapter 19 "Configuring HSRP" for more information.
•HTTP—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 4.x for more information.
•Licensing—See theCisco NX-OS Licensing Guide for more information.
•NetFlow—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for more information.
•NTP—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for more information.
•RADIUS—See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 4.x for more information.
•Ping and Traceroute —See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 4.x for more information.
•SSH—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 4.x for more information.
•SNMP—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for more information.
•Syslog—See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.xe for more information.
•TACACS+—See the Cisco Nexus 7000 Series NX-OS Security Configuration Guide, Release 4.x for more information.
•TFTP—See the Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 4.x for more information.
•VRRP—See Chapter 20 "Configuring VRRP" for more information.
•XML—See the Cisco Nexus 7000 Series NX-OS XML Management Interface User Guide 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:
•Combining Reachability and Filtering
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 14-3 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 14-3 Service VRF Reachability
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 14-4 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 14-4 Service VRF 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 14-5 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 14-5 Service VRF Reachability Filtering
The following table shows the licensing requirements for this feature:
VRFs have the following prerequisites:
•You must install the Advanced Services license to use VDCs besides the default VDC.
VRFs have the following 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.
This section contains the following topics:
•Assigning VRF Membership to an Interface
•Configuring VRF Parameters for a Routing Protocol
•Configuring a VRF-Aware Service
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.
You can create a VRF in a VDC.
Ensure that you are in the correct VDC (or use the switchto vdc command).
1. config t
2. vrf context vrf-name
3. configure optional parameters
4. show vrf [vrf-name]
5. copy running-config startup-config
Use the no vrf context command to delete the VRF and the associated configuration:
|
|
---|---|
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.
The following example shows how to create a VRF and add a static route to the VRF:
switch# config t
switch(config)# vrf context Enterprise
switch(config-vrf)# ip route 192.0.2.0/8 192.0.2.10
switch(config-vrf)# exit
switch(config)# copy running-config startup-config
You can make an interface a member of a VRF.
Ensure that you are in the correct VDC (or use the switchto vdc command).
Assign the IP address for an interface after you have configured the interface for a VRF.
1. config t
2. interface interface-type slot/port
3. vrf member vrf-name
4. ip-address ip-prefix/length
5. show vrf vrf-name interface interface-type number
6. copy running-config startup-config
The following example shows how to add an interface to the VRF:
switch# config t
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
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.
Ensure that you are in the correct VDC (or use the switchto vdc command).
1. config t
2. router protocol tag
3. vrf vrf-name
4. configure optional parameters for the protocol in the VRF.
5. copy running-config startup-config
The following example shows how to create a VRF and add an interface to the VRF:
switch# config t
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
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.
Ensure that you are in the correct VDC (or use the switchto vdc command).
1. config t
2. service parameters [filter_vrf vrf-name] [use-vrf vrf-name]
3. vrf context [vrf-name]
4. service parameters [all-vrfs][use-vrf vrf-name]
5. copy running-config startup-config
The following example shows how to send SNMP information for all VRFs to SNMP host 192.0.2.1, reachable on VRF Red:
switch# config t
switch(config)# snmp-server host 192.0.2.1 for-all-vrfs use-vrf Red
switch(config)# copy running-config startup-config
The following example shows how to Filter SNMP information for VRF Blue to SNMP host 192.0.2.12, reachable on VRF Red:
switch# config t
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
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:
|
|
---|---|
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:
|
|
---|---|
routing-context vrf default
Example: switch%red# routing-context vrf default switch# |
Sets the default routing context. |
To display VRF configuration information, use one of the following commands:
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
vrf Red
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
vrf context Green
!Create the OSPF instances and associate them with a single VRF or multiple VRFs
(recommended)
feature ospf
router ospf Lab
vrf Red
!
router ospf Production
vrf Blue
router-id 1.1.1.1
vrf Green
router-id 2.2.2.2
!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
!
interface ethernet 10/3
vrf member Green
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.
Use the SNMP context lab to access the OSPF-MIB values for the OSPF instance Lab in VRF Red in this example.
The following topics can give more information on VRFs:
•Cisco Nexus 7000 Series NX-OS Fundamentals Configuration Guide, Release 4.x
•Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x
Table 14-1 lists the default settings for VRF parameters.
|
|
---|---|
Configured VRFs |
default, management |
routing context |
default VRF |
For additional information related to implementing virtualization, see the following sections:
|
|
---|---|
VRF CLI |
Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference |
VDCs |
Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.x |
|
|
---|---|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
— |
Table 14-2 lists the release history for this feature.
|
|
|
---|---|---|
VRF |
4.0(1) |
This feature was introduced. |