Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 4.x

vPC Overview

A virtual port channel (vPC) allows links that are physically connected to two different Cisco Nexus 7000 Series devices to appear as a single port channel by a third device (see Figure 6-1). The third device can be a switch, server, or any other networking device that supports port channels. Beginning with Cisco NX-OS Release 4.1(4), you can configure up to 256 vPCs per device. A vPC can provide Layer 2 multipathing, which allows you to create redundancy and increase bisectional bandwidth by enabling multiple parallel paths between nodes and allowing load balancing traffic.

Figure 6-1 vPC Architecture

You can use only Layer 2 port channels in the vPC. A vPC domain is associated to a single VDC, so all vPC interfaces belonging to a given vPC domain must be defined in the same VDC. You must have a separate vPC peer-link and peer-keepalive link infrastructure for each VDC deployed. Consolidating a vPC pair (two vPC peer devices of the same domain) in two VDCs of the same physical device is not supported. The vPC peer link must use 10-Gigabit Ethernet ports for both ends of the link or the link will not form.

You configure the port channels by using one of the following:

• No protocol
• Link Aggregation Control Protocol (LACP)

When you configure the port channels in a vPC—including the vPC peer link channel—without using LACP, each device can have up to eight active links in a single port channel. When you configure the port channels in a vPC—including the vPC peer link channels—using LACP, each device can have eight active links and eight standby links in a single port channel. (See the “vPC Interactions with Other Features” section for more information on using LACP and vPCs.)

Note You must enable the vPC feature before you can configure or run the vPC functionality.

Beginning in Release 4.2, the system automatically takes a checkpoint prior to disabling the feature, and you can rollback to this checkpoint. See Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for information on rollbacks and checkpoints.

After you enable the vPC functionality, you create the peer-keepalive link, which sends heartbeat messages between the two vPC peer devices.

You can create a vPC peer link by configuring a port channel on one Cisco Nexus 7000 Series chassis by using the N7K-M132XP-12 module and two or more of the 10-Gigabit Ethernet ports in dedicated mode. To ensure that you have the correct hardware to enable and run vPC beginning with Cisco NX-OS Release 4.1(5), enter the show hardware feature-capability command. If you see an X across from vPC, your hardware cannot enable the vPC feature.

We recommend that you configure the vPC peer-link Layer 2 port channels as trunks. Then, on another Cisco Nexus 7000 Series chassis with an N7K-M132XP-12 module, you configure another port channel again using two or more of the 10-Gigabit Ethernet ports in dedicated mode. Connecting these two port channels creates a vPC peer link in which the two linked Nexus devices appear as one device to a third device. The third device, or downstream device, can be a switch, server, or any other networking device that uses a regular port channel to connect to the vPC. If you are not using the correct module, the system displays an error message.

Note We recommend that you configure the vPC peer links on dedicated ports of different N7K-M132XP-12 modules to reduce the possibility of a failure. For the best resiliency scenario, use at least two N7K-M132XP-12 modules.

Beginning with Cisco Release NX-OS 4.2, if you must configure all the vPC peer links and core-facing interfaces on a single N7K-M132XP-12 module, you should configure a track object that is associated with the Layer 3 link to the core and on all the links on the vPC peer link on both vPC peer devices. Once you configure this feature and if the primary vPC peer device fails, the system automatically suspends all the vPC links on the primary vPC peer device. This action forces all the vPC traffic to the secondary vPC peer device until the system stabilizes.

Create a track object and apply that object to all links on the primary vPC peer device that connect to the core and to the vPC peer link. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x for information on the track interface command.

The vPC domain includes both vPC peer devices, the vPC peer-keepalive link, the vPC peer link, and all of the port channels in the vPC domain connected to the downstream device. You can have only one vPC domain ID on each device.

In this version, you can connect each downstream device to a single vPC domain ID using a single port channel.

Note Always attach all vPC devices using port channels to both vPC peer devices.

A vPC (see Figure 6-2) provides the following benefits:

• Allows a single device to use a port channel across two upstream devices
• Eliminates Spanning Tree Protocol (STP) blocked ports
• Provides a loop-free topology
• Uses all available uplink bandwidth
• Provides fast convergence if either the link or a device fails
• Provides link-level resiliency
• Assures high availability

Figure 6-2 vPC Interfaces in One VDC

For more information on VDCs, see the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.x .

vPC Terminology

The terminology used in vPCs is as follows:

• vPC—The combined port channel between the vPC peer devices and the downstream device.
• vPC peer device—One of a pair of devices that are connected with the special port channel known as the vPC peer link.
• vPC peer link—The link used to synchronize states between the vPC peer devices. Both ends must be on 10-Gigabit Ethernet interfaces.
• vPC domain—This domain includes both vPC peer devices, the vPC peer-keepalive link, and all of the port channels in the vPC connected to the downstream devices. It is also associated to the configuration mode that you must use to assign vPC global parameters.
• vPC peer-keepalive link—The peer-keepalive link monitors the vitality of a vPC peer Cisco Nexus 7000 device. The peer-keepalive link sends configurable, periodic keepalive messages between vPC peer devices.

We recommend that you associate a peer-keepalive links to a separate VRF mapped to a Layer 3 interface in each vPC peer device. If you do not configure a separate VRF, the system uses the management VRF by default. However, if you use the management interfaces for the peer-keepalive link, you must put a management switch connected to both the active and standby management ports on each vPC peer device (see Figure 6-3).

Figure 6-3 Separate Switch Required to Connect Management Ports for vPC Peer-Keepalive Link

No data or synchronization traffic moves over the vPC peer-keepalive link; the only traffic on this link is a message that indicates that the originating switch is operating and running vPC.

• vPC member port—Interfaces that belong to the vPCs.

vPC Peer Links

A vPC peer link is the link that is used to synchronize the states between the vPC peer devices. Both ends of the link must be on 10-Gigabit Ethernet interfaces. A single vPC domain between two VDCs on the same physical Cisco Nexus 7000 device is not supported.

This section describes the vPC peer link and includes the following sections:

• vPC Peer-Link Overview
• Features That You Must Manually Configure on the Primary and Secondary Devices
• Configuring VLAN Interfaces for Layer 3 connectivity

Note You must configure the peer-keepalive link before you configure the vPC peer link or the peer link will not come up. (See “Peer-Keepalive Link and Messages” section for information on the vPC peer-keepalive link and messages.)

You can configure a vPC peer link to configure two devices as vPCs peers. You must use the N7K-M132XP-12 module in order to configure a vPC peer link.

Note We recommend that you use the dedicated port mode when you configure a vPC peer link. For information about the dedicated port mode, see Chapter2, “Configuring Basic Interface Parameters” We also recommend that you configure the vPC peer-link Layer 2 port channels as trunks.

vPC Peer Link and I/O Modules Support

Only identical I/O modules on either side of a vPC peer link are supported. Using different I/O modules on either side of a vPC peer link is not supported. Mixing I/O modules on the same side of a port channel is also not supported. Table 6-1 displays the I/O modules that are supported on both sides of a vPC peer link. Figure 6-4 to Figure 6-7 show the configurations that are supported and not supported on both sides of a vPC peer link.

Figure 6-4 Supported—Two F1 I/O Modules on Either Side of a vPC Peer Link

Figure 6-5 Supported—Two M1 I/O Modules on Either Side of a vPC Peer Link

Figure 6-6 Not Supported—Two Different I/O Modules on Either Side of a vPC Peer Link
(M1 and F1)

Figure 6-7 Not Supported—Mixing I/O Modules on the Same Side of a Peer Link

vPC Peer-Link Overview

You can have only two devices as vPC peers; each device can serve as a vPC peer to only one other vPC peer. The vPC peer devices can also have non-vPC links to other devices.

Note You must configure HSRP or any other first-hop redundancy protocol when you are using vPC. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x for details about configuring first-hop redundancy protocols.

See Figure 6-8 for invalid vPC peer configurations.

Figure 6-8 vPC Peer Configurations That Are Not Allowed

To make a valid configuration, you first configure a port channel on each device and then configure the vPC domain. You assign the port channel on each device as a peer link, using the same vPC domain ID. For redundancy, we recommend that you should configure at least two of the dedicated ports into the port channel because if one of the interfaces in the vPC peer link fails, the device automatically falls back to use another interface in the peer link.

Note We recommend that you configure the Layer 2 port channels in trunk mode.

Many operational parameters and configuration parameters must be the same in each device connected by a vPC peer link (see the “Compatibility Parameters for vPC Peer Links” section). Because each device is completely independent on the management plane, you must ensure that the devices are compatible on the critical parameters. vPC peer devices have separate control planes. After configuring the vPC peer link, you should display the configuration on each vPC peer device to ensure that the configurations are compatible.

Note You must ensure that the two devices connected by the vPC peer link have certain identical operational and configuration parameters. For more information on required configuration consistency, see the “Compatibility Parameters for vPC Peer Links” section.

When you configure the vPC peer link, the vPC peer devices negotiate that one of the connected devices is the primary device and the other connected device is the secondary device (see the “Configuring vPCs” section). The Cisco NX-OS software uses the lowest MAC address to elect the primary device. The software takes different actions on each device—that is, the primary and secondary—only in certain failover conditions. If the primary device fails, the secondary device becomes the new primary device when the system recovers, and the previously primary device is now the secondary device.

You can also configure which of the vPC devices is the primary device. Changing the priority of the vPC peer devices can cause the interfaces in your network to go up and down. If you want to configure the role priority again to make one vPC device the primary device, configure the role priority on both the primary and secondary vPC devices with the appropriate values. Then, shut down the port channel that is the vPC peer link on both devices by entering the shutdown command , and finally re-enable the port channel on both devices by enter the no shutdown command.

Note We recommend that you use two different modules for redundant on each vPC peer device vPC peer links.

The software keeps all traffic that forwards across the vPC peer devices as local traffic. A packet that ingresses the port channel uses one of the local links rather than moving across the vPC peer link. Unknown unicast, multicast, and broadcast traffic (including STP BPDUs) are flooded across the vPC peer link. The software keeps the multicast forwarding state synchronized on both of the vPC peer devices.

You can configure any of the standard load-balancing schemes on both the vPC peer link devices and the downstream device (see Chapter 5, “Configuring Port Channels” for information on load balancing).

Configuration information flows across the vPC peer links using the Cisco Fabric Service over Ethernet (CFSoE) protocol. (See the “CFSoE” section for more information about CFSoE.)

All MAC addresses for those VLANs configured on both devices are synchronized between vPC peer devices. The software uses CFSoE for this synchronization. (See the “CFSoE” section for information about CFSoE.)

Beginning with Cisco NX-OS 4.2(1), you can configure vPC peer devices to act as the gateway even for packets that are destined to the vPC peer device’s MAC address.

Use the peer-gateway command to configure this feature.

If the vPC peer link fails, the software checks the status of the remote vPC peer device using the peer-keepalive link, which is a link between vPC peer devices that ensures that both devices are up. If the vPC peer device is up, the secondary vPC device disables all vPC ports on its device, to prevent loops and disappearing or flooding traffic. The data then forwards down the remaining active links of the port channel.

Note We recommend that you create and configure a separate VRF and configure a Layer 3 port on each vPC peer device in that VRF for the vPC peer-keepalive link. The default ports and VRF for the peer-keepalive are the management ports and VRF.

The software learns of a vPC peer device failure when the keepalive messages are not returned over the peer-keepalive link.

Use a separate link (vPC peer-keepalive link) to send configurable keepalive messages between the vPC peer devices. The keepalive messages on the vPC peer-keepalive link determines whether a failure is on the vPC peer link only or on the vPC peer device. The keepalive messages are used only when all the links in the peer link fail. See the “Peer-Keepalive Link and Messages” section for information about the keepalive message.

Features That You Must Manually Configure on the Primary and Secondary Devices

You must manually configure the following features to conform to the primary/secondary mapping of each of the vPC peer devices:

• STP root—Configure the primary vPC peer device as the STP primary root device and configure the vPC secondary device to be the STP secondary root device. See the “vPC Peer Links and STP” section for more information on vPC and STP.

– We recommend that you configure the vPC peer link interfaces as STP network ports so that Bridge Assurance is enabled on all vPC peer links

– We recommend that you configure Rapid PVST+ so that the primary device is the root for all VLANs and configure MST so that the primary device is the root for all instances.

• Layer 3 VLAN network interface—Configure Layer 3 connectivity from each vPC peer device by configuring a VLAN network interface for the same VLAN from both devices.
• HSRP active—If you want to use HSRP and VLAN interfaces on the vPC peer devices, configure the primary vPC peer device with the HSRP active highest priority. Configure the secondary device to be the HSRP standby. And ensure that you have VLAN interfaces on each vPC device that are in the same administrative and operational mode. (See the “vPC Peer Links and Routing” section for more information on vPC and HSRP.)

See the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 4.x for information on configuring UDLD.

Configuring VLAN Interfaces for Layer 3 connectivity

You can use VLAN network interfaces on the vPC peer devices to link to Layer 3 of the network for such applications as HSRP and PIM. However, we recommend that you configure a separate Layer 3 link for routing from the vPC peer devices, rather than using a VLAN network interface for this purpose.

Note Ensure that you have a VLAN network interface configured on each peer device and that the interface is connected to the same VLAN on each device. Also, each VLAN interface must be in the same administrative and operational mode. For more information on configuring VLAN network interfaces, see Chapter4, “Configuring Layer 3 Interfaces”

If a failover occurs on the vPC peer link, the VLAN interfaces on the vPC peer devices are also affected. If a vPC peer link fails, the system brings down associated VLAN interfaces on the secondary vPC peer device.

Beginning with Cisco NX-OS 4.2(1), you can ensure that specified VLAN interfaces do not go down on the vPC secondary device when the vPC peer link fails.

Use the dual-active exclude interface-vlan command to configure this feature.

Note When you attach a Layer 3 device to a vPC domain, the peering of routing protocols using a VLAN also carried on the vPC peer-link is not supported. If routing protocol adjacencies are needed between vPC peer devices and a generic Layer 3 device, you must use physical routed interfaces for the interconnection. Use of the vPC peer-gateway feature does not change this requirement.

Peer-Keepalive Link and Messages

The Cisco NX-OS software uses the peer-keepalive link between the vPC peers to transmit periodic, configurable keepalive messages. You must have Layer 3 connectivity between the peer devices to transmit these messages; the system cannot bring up the vPC peer link unless the peer-keepalive link is already up and running.

Note We recommend that you associate the vPC peer-keepalive link to a separate VRF mapped to a Layer 3 interface in each vPC peer device. If you do not configure a separate VRF, the system uses the management VRF and management ports by default. Do not use the peer link itself to send and receive vPC peer-keepalive messages.
For more information on configuring VRFs, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x.

If one of the vPC peer devices fails, the vPC peer device on the other side of the vPC peer link senses the failure by not receiving any peer-keepalive messages. The default interval time for the vPC peer-keepalive message is 1 second, and you can configure the interval between 400 milliseconds and 10 seconds.

You can configure a hold-timeout value with a range of 3 to 10 seconds; the default hold-timeout value is 3 seconds. This timer starts when the vPC peer link goes down. During this hold-timeout period, the secondary vPC peer device ignores vPC peer-keepalive messages, which ensures that network convergence occurs before vPC action takes place. The purpose of the hold-timeout period is to prevent false-positive cases.

You can also configure a timeout value with a range of 3 to 20 seconds; the default timeout value is 5 seconds. This timer starts at the end of the hold-timeout interval. During the timeout period, the secondary vPC peer device checks for vPC peer-keepalive hello messages from the primary vPC peer device. If the secondary vPC peer device receives a single hello message, that device disables all vPC interfaces on the secondary vPC peer device.

The difference between the hold-timeout and the timeout parameters is as follows:

• During the hold-timeout, the vPC secondary device does not take any action based on any keepalive messages received. This is to prevent the system taking action when the keepalive might be received just temporarily, such as if a supervisor fails a few seconds after the peer link goes down.
• During the timeout, the vPC secondary device takes action to become the vPC primary device if no keepalive message is received by the end of the configured interval.

See the “Configuring vPCs” section for information on configuring the timer for the keepalive messages.

Note Ensure that both the source and destination IP addresses used for the peer-keepalive messages are unique in your network and these IP addresses are reachable from the VRF associated with the vPC peer-keepalive link.

Use the command-line interface (CLI) to configure the interfaces you are using the vPC peer-keepalive messages as trusted ports. Leave the precedence at the default (6) or configure it higher. The following is an example of configuring an interface as a trusted port:

See the Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide, Release 4.x for complete information on configuring trusted ports and precedence.

vPC Peer-Gateway

Beginning with Cisco NX-OS 4.2(1), you can configure vPC peer devices to act as the gateway even for packets that are destined to the vPC peer device's MAC address. Use the peer-gateway command to configure this feature.

Some network-attached storage (NAS) devices or load-balancers may have features aimed to optimize the performances of particular applications. Essentially these features avoid performing a routing-table lookup when responding to a request that originated form a host not locally attached to the same subnet. Such devices may reply to traffic using the MAC address of the sender Cisco Nexus 7000 device rather than the common HSRP gateway. Such behavior is non-complaint with some basic Ethernet RFC standards. Packets reaching a vPC device for the non-local router MAC address are sent across the peer-link and could be dropped by the built in vPC loop avoidance mechanism if the final destination is behind another vPC.

The vPC peer-gateway capability allows a vPC switch to act as the active gateway for packets that are addressed to the router MAC address of the vPC peer. This feature enables local forwarding of such packets without the need to cross the vPC peer-link. In this scenario, the feature optimizes use of the peer-link and avoids potential traffic loss.

Configuring the peer-gateway feature needs to be done on both primary and secondary vPC peers and is non-disruptive to the operations of the device or to the vPC traffic. The vPC peer-gateway feature can be configured globally under the vPC domain submode.

When enabling this feature it is also required to disable IP redirects on all interface VLANs mapped over a vPC VLAN to avoid generation of IP redirect messages for packets switched through the peer gateway router. When the feature is enabled in the vPC domain, the user is notified of such a requirement through an appropriate message.

Packets arriving at the peer-gateway vPC device will have their TTL decremented, so packets carrying TTL = 1 may be dropped in transit due to TTL expire. This needs to be taken into account when the peer-gateway feature is enabled and particular network protocols sourcing packets with TTL = 1 operate on a vPC VLAN.

vPC Domain

You can use the vPC domain ID to identify the vPC peer links and the ports that are connected to the vPC downstream devices.

The vPC domain is also a configuration mode that you use to configure the keepalive messages, and configure other vPC peer link parameters rather than accept the default values. See the “Configuring vPCs” section for more information on configuring these parameters.

To create a vPC domain, you must first create a vPC domain ID on each vPC peer device using a number from 1 to 1000. You can have only one vPC domain per VDC.

You must explicitly configure the port channel that you want to act as the peer link on each device. You associate the port channel that you made a peer link on each device with the same vPC domain ID to form a single vPC domain. Within this domain, the system provides a loop-free topology and Layer 2 multipathing.

You can only configure these port channels and vPC peer links statically. All ports in the vPC on each of the vPC peer devices must be in the same VDC. You can configure the port channels and vPC peer links either using LACP or no protocol. When possible, we recommend that you use LACP with the interfaces in active mode to configure port channels in each vPC. This ensures an optimized, graceful recovery in a port-channel failover scenario and provides configuration checks against configuration mismatch among the port channels themselves.

The vPC peer devices use the vPC domain ID that you configure to automatically assign a unique vPC system MAC address. Each vPC domain has a unique MAC address that is used as a unique identifier for the specific vPC-related operations, although the devices use the vPC system MAC addresses only for link-scope operations, such as LACP. We recommend that you create each vPC domain within the contiguous Layer 2 network with a unique domain ID. You can also configure a specific MAC address for the vPC domain, rather than having the Cisco NX-OS software assign the address.

See the “CFSoE” section for more information on displaying the vPC MAC table.

After you create a vPC domain, the Cisco NX-OS software creates a system priority for the vPC domain. You can also configure a specific system priority for the vPC domain.

Note When manually configuring the system priority, you must ensure that you assign the same priority value on both vPC peer devices. If the vPC peer devices have different system priority values, vPC will not come up.

Compatibility Parameters for vPC Peer Links

Many configuration and operational parameters must be identical on all interfaces in the vPC. We recommend that you configure the Layer 2 port channels that you use for the vPC peer link in trunk mode.

After you enable the vPC feature and configure the peer link on both vPC peer devices, CFS messages provide a copy of the configuration on the local vPC peer device configuration to the remote vPC peer device. The system then determines whether any of the crucial configuration parameters differ on the two devices. (See the “CFSoE” section for more information on CFS.)

Note Enter the show vpc consistency-parameters command to display the configured values on all interfaces in the vPC. The displayed configurations are only those configurations that would limit the vPC peer link and vPC from coming up.

The compatibility check process for vPCs differs from the compatibility check for regular port channels. See Chapter 5, “Configuring Port Channels” for information on regular port channels.

This section includes the following sections:

• Configuration Parameters That Must Be Identical
• Configuration Parameters That Should Be Identical

Configuration Parameters That Must Be Identical

The configuration parameters in this section must be configured identically on both devices of the vPC peer link or the vPC moves into suspend mode.

Note You must ensure that all interfaces in the vPC have the identical operational and configuration parameters listed below.

Note Enter the show vpc consistency-parameters command to display the configured values on all interfaces in the vPC. The displayed configurations are only those configurations that would limit the vPC peer link and vPC from coming up.

The devices automatically check for compatibility for some of these parameters on the vPC interfaces. The per-interface parameters must be consistent per interface, and the global parameters must be consistent globally:

• Port-channel mode: on, off, or active
• Link speed per channel
• Duplex mode per channel
• Trunk mode per channel:

– Native VLAN

– VLANs allowed on trunk

– Tagging of native VLAN traffic

• Spanning Tree Protocol (STP) mode
• STP region configuration for Multiple Spanning Tree
• Enable/disable state per VLAN
• STP global settings:

– Bridge Assurance setting

– Port type setting

– Loop Guard settings

• STP interface settings:

– Port type setting

– Loop Guard

– Root Guard

• Maximum Transmission Unit (MTU)

If any of these parameters are not enabled or defined on either device, the vPC consistency check ignores those parameters.

Note To ensure that none of the vPC interfaces are in the suspend mode, enter the show vpc brief and show vpc consistency-parameters commands and check the syslog messages.

Configuration Parameters That Should Be Identical

When any of the following parameters are not configured identically on both vPC peer devices, a misconfiguration may cause undesirable behavior in the traffic flow:

• MAC aging timers
• Static MAC entries
• VLAN interface—Each device on the end of the vPC peer link must have a VLAN interface configured for the same VLAN on both ends and they must be in the same administrative and operational mode. Those VLANs configured on only one device of the peer link do not pass traffic using the vPC or peer link. You must create all VLANs on both the primary and secondary vPC devices, or the VLAN will be suspended.
• All ACL configurations and parameters
• Quality of Service (QoS) configuration and parameters
• STP interface settings:

– BPDU Filter

– BPDU Guard

– Cost

– Link type

– Priority

– VLANs (Rapid PVST+)

• Port security
• Cisco Trusted Security (CTS)
• Dynamic Host Configuration Protocol (DHCP) snooping
• Network Access Control (NAC)
• Dynamic ARP Inspection (DAI)
• IP source guard (IPSG)
• Internet Group Management Protocol (IGMP) snooping
• Hot Standby Routing Protocol (HSRP)
• Protocol Independent Multicast (PIM)
• Gateway Load-Balancing Protocol (GLBP)
• All routing protocol configurations

To ensure that all the configuration parameters are compatible, we recommend that you display the configurations for each vPC peer device once you configure the vPC.

vPC Number

Once you have created the vPC domain ID and the vPC peer link, you create port channels to attach the downstream device to each vPC peer device. That is, you create one port channel to the downstream device from the primary vPC peer device and you create another port channel to the downstream device from the secondary peer device.

Note We recommend that you configure the ports on the downstream devices that connect to a host or a network device that is not functioning as a switch or a bridge as STP edge ports. See Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.x for more information on STP port types.

Finally, working on each vPC peer device, you assign a vPC number to the port channel that connects to the downstream device. You will experience minimal traffic disruption when you are creating vPCs. To simplify the configuration, you can assign the vPC ID number to every port channel to be the same as the port channel itself (that is, vPC ID 10 for port channel 10).

Note The vPC number that you assign to the port channel connecting to the downstream device from the vPC peer device must be identical on both vPC peer devices.

Moving Other Port Channels into a vPC

Note You must attach a downstream device using a port channel to both the vPC peer devices.

To connect to the downstream device, you create a port channel to the downstream device from the primary vPC peer device and you create another port channel to the downstream device from the secondary peer device. Finally, working on each vPC peer device, you assign a vPC number to the port channel that connects to the downstream device. You will experience minimal traffic disruption when you are creating vPCs.

Configuring vPC Peer Links and Links to the Core on a Single Module

Note We recommend that you configure the vPC peer links on dedicated ports of different N7K-M132XP-12 modules to reduce the possibility of a failure. For the best resiliency scenario, use at least two N7K-M132XP-12 modules.

Beginning with Cisco NX-OS Release 4.2, if you must configure all the vPC peer links and core-facing interfaces on a single N7K-M132XP-12 module, you should configure, using the command line interface, a track object and a track list that is associated with the Layer 3 link to the core and on all vPC peer links on both vPC peer devices. You use this configuration to avoid dropping traffic if that particular module goes down because when all the tracked objects on the track list go down, the system does the following:

• Stops the vPC primary peer device sending peer-keepalive messages which forces the vPC secondary peer device to take over.
• Brings down all the downstream vPCs on that vPC peer device, which forces all the traffic to be rerouted in the access switch toward the other vPC peer device.

Once you configure this feature and if the module fails, the system automatically suspends all the vPC links on the primary vPC peer device and stops the peer-keepalive messages. This action forces the vPC secondary device to take over the primary role and all the vPC traffic to go to this new vPC primary device until the system stabilizes.

Create a track list that contains all the links to the core and all the vPC peer links as its object. Enable tracking for the specified vPC domain for this track list. Apply this same configuration to the other vPC peer device. See the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x , for information about configuring object tracking and track lists.

See the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x , for information on configuring object tracking.

Note Ensure that you use the Boolean OR when you configure the objecting-tracking list.

Sample configuration is as follows:

Step 1. Configure track objects on an interface (Layer 3 to core) and on a port channel (vPC peer link).

Step 2. Create a track list that contains all the interfaces in the track list using the Boolean OR.

Step 3. Add this track object to the vPC domain:

Step 4. This example shows how to display the track object using the show vpc brief command.

This example shows how to display information about the track objects using the show track brief command.

Note The vPC object tracking feature can also be used in the case where you have multiple modules.

One potential application is to track power outages on the vPC peer switches. If this event occurs, the affected switch powers off all its line cards but its supervisor remains up. If the vPC peer-keepalive is configured on the mgmt0 interface of the supervisor, the keepalive messages continue and its vPC peer switch is not notified of the power failure. However the peer switch will detect that the vPC peer-link is down. As a consequence, the vPC peer switch will shut all its member ports.

If the switch that suffers the power outage is the vPC primary switch, the result is all vPC traffic is lost. To remedy this scenario, use the object tracking feature to detect when vPC peer-link and uplink ports are down. If both failures occur, the vPC object tracking will suspend sending peer-keepalive messages on the mgmt0 interface. The vPC secondary switch will continue forwarding traffic while the primary switch is out of service.

vPC Interactions with Other Features

This section includes the following topics:

• vPC and LACP
• vPC Peer Links and STP
• vPC Peer Switch
• vPC and ARP or ND
• vPC Multicast—PIM, IGMP, and IGMP Snooping
• vPC Peer Links and Routing
• CFSoE

vPC and LACP

LACP uses the system MAC address of the vPC domain to form the LACP Aggregation Group (LAG) ID for the vPC. (See Chapter 5, “Configuring Port Channels” for information on LAG-ID and LACP.)

You can use LACP on all the vPC port channels, including those channels from the downstream device. We recommend that you configure LACP with active mode on the interfaces on each port channel on the vPC peer devices. This configuration allows you to more easily detect compatibility between devices, unidirectional links, and multihop connection, and provides dynamic reaction to run-time changes and link failures.

The vPC peer link supports 16 LACP interfaces: 8 active links and 8 hot standby links. You can configure 16 LACP links on the downstream vPC channel: 8 active links and 8 hot standby links. If you configure the port channels without using LACP, you can have only 8 links in each channel

We recommend that you manually configure the system priority on the vPC peer-link devices to ensure that the vPC peer-link devices have a higher LACP priority than the downstream connected devices. A lower numerical value system priority means a higher LACP priority.

Note When manually configuring the system priority, you must ensure that you assign the same priority value on both vPC peer devices. If the vPC peer devices have different system priority values, vPC will not come up.

vPC Peer Links and STP

When you first bring up vPC, STP reconverges. STP treats the vPC peer link as a special link and always includes the vPC peer link in the STP active topology.

We recommend that you set all the vPC peer link interfaces to the STP network port type so that Bridge Assurance is automatically enabled on all vPC peer links. We also recommend that you do not enable any of the STP enhancement features on vPC peer links. It will not cause any problems if the STP enhancements are already configured, but you need not configure these.

When you are running both MST and Rapid PVST+, ensure that the PVST simulation feature is correctly configured.

See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.x for information on STP enhancement features and PVST simulation.

Note You must configure a list of parameters to be identical on the vPC peer devices on both sides of the vPC peer link. See the “Compatibility Parameters for vPC Peer Links” section for information about these required matched settings.

STP is distributed; that is, the protocol continues running on both vPC peer devices. However, the configuration on the vPC peer device elected as the primary device controls the STP process for the vPC interfaces on the secondary vPC peer device.

The primary vPC device synchronizes the STP state on the vPC secondary peer device using Cisco Fabric Services over Ethernet (CFSoE). See the “CFSoE” section for information on CFSoE.

The STP process for vPC also relies on the periodic keepalive messages to determine when one of the connected devices on the peer link fails. See the “Peer-Keepalive Link and Messages” section for information on these messages.

The vPC manager performs a proposal/handshake agreement between the vPC peer devices that set the primary and secondary devices and coordinates the two devices for STP. The primary vPC peer device then controls the STP protocol on both the primary and secondary devices. We recommend that you configure the primary vPC peer device as the STP primary root device and configure the secondary VPC device to be the STP secondary root device.

If the primary vPC peer device fails over to the secondary vPC peer device, there is no change in the STP topology.

The BPDUs uses the MAC address set for the vPC for the STP bridge ID in the designated bridge ID field. The vPC primary device sends these BPDUs on the vPC interfaces.

You must configure both ends of vPC peer link with the identical STP configuration for the following parameters:

• STP global settings:

– STP mode

– STP region configuration for MST

– Enable/disable state per VLAN

– Bridge Assurance setting

– Port type setting

– Loop Guard settings

• STP interface settings:

– Port type setting

– Loop Guard

– Root Guard

Note If any of these parameters are misconfigured, the Cisco NX-OS software suspends all interfaces in the vPC. Check the syslog and enter the show vpc brief command to see if the vPC interfaces are suspended.

Ensure that the following STP interface configurations are identical on both sides of the vPC peer links or you may see unpredictable behavior in the traffic flow:

• BPDU Filter
• BPDU Guard
• Cost
• Link type
• Priority
• VLANs (PVRST+)

Note Display the configuration on both sides of the vPC peer link to ensure that the settings are identical.

You can use the show spanning-tree command to display information about the vPC, when that feature is enabled. See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.x for an example.

Note We recommend that you configure the ports on the downstream devices as STP edge ports. You should configure all host ports connected to a switch as STP edge ports. (See Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.x for more information on STP port types.)

Note When migrating from vPC+ to vPC topology, spanning-tree bridge-assurance command should be enabled on vPC peer-link for the transition to work.

vPC Peer Switch

The vPC peer switch feature was back-ported to Cisco NX-OS Release 4.2(6) to address performance concerns around STP convergence. This feature allows a pair of Cisco Nexus 7000 Series devices to appear as a single STP root in the Layer 2 topology. This feature eliminates the need to pin the STP root to the vPC primary switch and improves vPC convergence if the vPC primary switch fails.

To avoid loops, the vPC peer link is excluded from the STP computation. In vPC peer switch mode, STP BPDUs are sent from both vPC peer devices to avoid issues related to STP BPDU timeout on the downstream switches, which can cause traffic disruption.

This feature can be used with these topologies:

• The pure peer switch topology in which the devices all belong to the vPC.
• The hybrid peer switch topology in which there is a mixture of vPC and non-vPC devices in the configuration.

Note If the vPC peer-link and vPC peer-keepalive link fail in a hybrid peer-switch configuration, you can lose traffic. In this scenario, the vPC peers use the same STP root ID as well same bridge ID. The access switch traffic is split in two with half going to the first vPC peer and the other half to the second vPC peer. With the peer link failed, there is no impact on north/south traffic but east-west traffic will be lost (black-holed).

See the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.x for information on STP enhancement features and Rapid PVST+.

vPC and ARP or ND

A feature was added to Cisco NX-OS Release 4.2(6) to address table synchronization across vPC peers using the reliable transport mechanism of the Cisco Fabric Service over Ethernet (CFSoE) protocol. The ip arp synchronize and ipv6 nd synchronize commands must be enabled and support faster convergence of address tables between the vPC peers. This convergence is designed to overcome the delay involved in ARP table restoration for IPv4 or ND table restoration for IPv6 when the peer-link port-channel flaps or when a vPC peer comes back online.

vPC Multicast—PIM, IGMP, and IGMP Snooping

Note Cisco NX-OS software for the Nexus 7000 Series devices does not support PIM SSM or BIDR on vPC. Cisco NX-OS software fully supports PIM ASM on vPC.

The software keeps the multicast forwarding state synchronized on both of the vPC peer devices. The IGMP snooping process on a vPC peer device shares the learned Group information with the other vPC peer device through the vPC peer link; the multicast states are always synchronized on both vPC peer devices. The PIM process in vPC mode ensures that only one of the vPC peer devices forwards the multicast traffic to the receivers.

Each vPC peer is a Layer 2 or Layer 3 device. Multicast traffic flows from only one of the vPC peer devices. You may see duplicate packets in the following scenarios:

• Orphan hosts
• When the Source and Receivers are in the Layer 2 vPC cloud in different VLANs with multicast routing enabled and a vPC member link goes down.

You may see negligible traffic loss in the following scenarios:

• When you reload the vPC peer device that is forwarding the traffic.
• When you restart PIM on the vPC peer device that is forwarding the traffic.

Ensure that you dual-attach all Layer 3 devices to both vPC peer devices. If one vPC peer device goes down, the other vPC peer device continues to forward all multicast traffic normally.

See the Cisco Nexus 7000 Series NX-OS Interfaces Command Reference, Release 4.x for information on commands that display information on vPC and multicast.

The following discusses vPC PIM and vPC IGMP/IGMP snooping:

• vPC PIM—The PIM process in vPC mode ensures that only one of the vPC peer devices forwards multicast traffic. The PIM process in vPC mode synchronizes the source state with both vPC peer devices and elects with vPC peer device forwards the traffic.
• vPC IGMP/IGMP snooping—The IGMP process in vPC mode synchronizes the DR information on both vPC peer devices. There is a dual-DR concept for IGMP when you are in vPC mode, which is not available when not in vPC mode, that has both vPC peer devices maintain the multicast group information between the peers.

You should enable or disable IGMP snooping identically on both vPC peer devices, and all the feature configurations should be identical. IGMP snooping is on by default.

See the Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide, Release 4.x for more information on multicasting.

Multicast PIM Dual DR (proxy DR )

By default, a multicast router sends PIM joins upstream only if it has interested receivers. These interested receivers can either be IGMP hosts (they communicate through IGMP reports) or other multicast routers (they communicate through PIM joins).

In the Cisco NX-OS vPC implementation (in non-F2 mode), PIM works in Dual designated router (DR) mode. That is, if a vPC device is a DR on a vPC SVI OIF, its peer automatically assumes the proxy DR role. IGMP adds an OIF (the report is learned on that OIF) to the forwarding if the OIF is a DR. With Dual DR, both vPC devices have an identical (*,G) entry with respect to the vPC SVI OIFs, as displayed in the following example:

IP PIM PRE-BUILD SPT

When the multicast source is in a Layer 3 cloud (outside the vPC domain), one vPC peer is elected as the forwarder for the source. This forwarder election is based on the metrics to reach the source. If there is a tie, the vPC primary is chosen as the forwarder. Only the forwarder has the vPC OIFs in its associated (S,G) and the nonforwarder (S,G) has 0 OIFs. Therefore, only the forwarder sends PIM (S,G) joins towards the source, as displayed in the following example:

In case of a failure (for example, a Layer 3 RPF link on the forwarder becomes inoperational or the forwarder gets reloaded), if the current nonforwarder ends up becoming the forwarder, it has to start sending PIM joins for (S,G) toward the source to pull the traffic. Depending upon the number of hops to reach the source, this operation might take some time (PIM is a hop by hop protocol).

To eliminate this issue and get better convergence, use the ip pim pre-build-spt command. This command enables PIM send joins even if the multicast route has 0 OIFs. In a vPC device, the nonforwarder sends PIM (S,G) joins upstream towards the source. The downside is that the link bandwidth upstream from the nonforwarder gets used for the traffic that is ultimately dropped by it, but the benefits that result with better convergence far outweigh the link bandwidth usage. Therefore, we recommend that all vPC customers use this command.

vPC Peer Links and Routing

The First Hop Routing Protocols (FHRP) interoperate with vPCs. The Hot Standby Routing Protocol (HSRP), Gateway Load Balancing Protocol (GLBP), and Virtual Router Redundancy Protocol (VRRP) all interoperate with vPCs. We recommend that you dual-attach all Layer 3 devices to both vPC peer devices.

Note You must enable the Layer 3 connectivity from each vPC peer device by configuring a VLAN network interface for the same VLAN from both devices. (See “Configuring Layer 3 Interfaces,” for information about creating VLAN network interfaces.)

The primary FHRP device responds to ARP requests, even though the secondary vPC device forwards the data traffic.

To simplify initial configuration verification and vPC/HSRP troubleshooting, you can configure the primary vPC peer device with the FHRP active router highest priority.

In addition, you can use the priority command in the if-hsrp configuration mode to configure failover thresholds for when a group state enabled on a vPC peer link is in standby or in listen state. You can configure lower and upper thresholds to prevent the interface from going up and down.

VRRP acts similarly to HSRP when running on vPC peer devices. You should configure VRRP the same way that you configure HSRP. For GLBP, the forwarders on both vPC peer devices forward traffic.

When the primary vPC peer device fails over to the secondary vPC peer device, the FHRP traffic continues to flow seamlessly.

Configure a separate Layer 3 link for routing from the vPC peer devices, rather than using a VLAN network interface for this purpose.

We do not recommend configuring the burnt-in MAC address option (use-bia) for HSRP or manually configuring virtual MAC addresses for any FHRP protocol in a vPC environment because these configurations can adversely affect the vPC load balancing. The hsrp use-bia command is not supported on vPCs. When you are configuring custom MAC addresses, you must configure the same MAC address on both vPC peer devices.

Beginning with Cisco NX-OS 4.2(1), you can configure a restore timer that will delay the vPC coming back up until after the peer adjacency forms and the VLAN interfaces are back up. This feature avoids packet drops when the routing tables may not be converged before the vPC is once again passing traffic.

Use the delay restore command to configure this feature.

Note In the event of a data center outage, if the HSRP is enabled before the vPC has successfully come up, traffic loss can occur. You need to enable an HSRP delay to give the vPC time to stabilize. If you enable both an HSRP delay and a preemption delay then the Cisco Nexus 7000 Series devices will allow Layer 2 switching only after both timers expire.

See the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x for more information on FHRPs and routing.

CFSoE

The Cisco Fabric Services over Ethernet (CFSoE) is a reliable state transport mechanism that is used to synchronize the actions of the vPC peer devices. CFSoE carries messages and packets for many features linked with vPC, such as STP and IGMP. Information is carried in CFS/CFSoE protocol data units (PDUs).

When you enable the vPC feature, the device automatically enables CFSoE, and you do not have to configure anything. CFSoE distributions for vPCs do not need the capabilities to distribute over IP or the CFS regions. You need not configure anything for the CFSoE feature to work correctly on vPCs.

The CFSoE transport is local to each VDC.

You can use the show mac address-table command to display the MAC addresses that CFSoE synchronizes for the vPC peer link.

Note Do not enter the no cfs eth distribute or the no cfs distribute command. You must enable CFSoE for vPC functionality. If you do enter either of these commands with vPC enabled, the system displays an error message.

When you enter the show cfs application command, the output displays “Physical-eth,” which shows the applications that are using CFSoE.

Cisco Fabric Services also transports data over TCP/IP. See the Cisco Nexus 7000 Series NX-OS System Management Configuration Guide, Release 4.x for more information on CFS over IP.

Note The software does not support CFS regions.

Virtualization Support

Note You must provision separate vPC peer-link and peer-keepalive link infrastructures for each vPC domain deployed in a given VDC.
Consolidating a vPC pair (two vPC peer devices of the same domain) in two VDCs of the same physical device is not supported.

All ports in a given vPC must be in the same VDC. This version of the software supports only one vPC per VDC. You can use the numbers from 1 to 4096 in each VDC to number the vPC and you can reuse these vPC numbers in a different VDC.

Note See the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.x for complete information on VDCs and assigning resources.

High Availability

During an In-Service Software Upgrade (ISSU), the software reload process on the first vPC device locks its vPC peer device using CFS messaging over the vPC communications channel. Only one device at a time is upgraded. When the first device has completed its upgrade, it unlocks its peer device. The second device then performs the upgrade process, locking the first device as it does so. During the upgrade, the two vPC devices will temporarily be running different releases of Cisco NX-OS, however the system functions correctly because of its backward compatibility support.

Note See the Cisco Nexus 7000 Series NX-OS High Availability and Redundancy Guide, Release 4.x for complete information on high-availability features.

Enabling vPCs

You must enable the vPC functionality before you can configure and use vPCs.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. feature vpc

3. exit

4. show feature

5. copy running-config startup-config

DETAILED STEPS

This example shows how to enable the vPC feature:

Disabling vPCs

Note When you disable the vPC functionality, the device clears all the vPC configurations.

BEFORE YOU BEGIN

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. no feature vpc

3. exit

4. show feature

5. copy running-config startup-config

DETAILED STEPS

This example shows how to disable the vPC feature:

Creating a vPC Domain and Entering the vpc-domain Mode

You can create a vPC domain and put the vPC peer link port channels into the identical vPC domain on both vPC peer devices. Use a unique vPC domain number throughout a single VDC. This domain ID is used to automatically to form the vPC system MAC address.

You can also use this command to enter the vpc-domain command mode.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. exit

4. show vpc brief

5. copy running-config startup-config

DETAILED STEPS

This example shows how to create a vPC domain:

This example shows how to enter the vpc-domain command mode to configure an existing vPC domain:

Configuring the vPC Keepalive Link and Messages

Note You must configure the vPC peer-keepalive link before the system can form the vPC peer link.

You can configure the destination IP for the peer-keepalive link that carries the keepalive messages. Optionally, you can configure other parameters for the keepalive messages.

Note We recommend that you configure a separate Virtual Routing and Forwarding (VRF) instance and put a Layer 3 port from each vPC peer device into that VRF for the vPC peer-keepalive link. Do not use the peer link itself to send vPC peer-keepalive messages. For information on creating and configuring VRFs, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x.
Ensure that both the source and destination IP addresses use for the peer-keepalive message are unique in your network.

The management port and management VRF are the defaults for these keepalive messages.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. peer-keepalive destination ip address [ hold-timeout secs | interval msecs { timeout secs} | { precedence {prec-value | network | internet | critical | flash - override | flash | immediate | priority | routine }} | { tos {tos-value | max-reliability | max-throughput | min-delay | min-monetary-cost | normal }} | tos-byte tos-byte-value} | source ipaddress | udp-port number | vrf {name | management | vpc-keepalive }]

4. exit

5. show vpc statistics

6. copy running-config startup-config

DETAILED STEPS

For more information on configuring VRFs, see the Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x .

This example shows how to configure the destination and source IP address and VRF for the vPC-peer-keepalive link:

Creating the vPC Peer Link

You create the vPC peer link by designating the port channel that you want on each device as the peer link for the specified vPC domain. We recommend that you configure the Layer 2 port channels that you are designating as the vPC peer link in trunk mode and that you use two ports on separate modules on each vPC peer device for redundancy.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are using a Layer 2 port channel.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. interface port-channel channel-number

3. (Optional) switchport mode trunk

4. (Optional) switchport trunk allowed vlan vlan-list

5. vpc peer-link

6. exit

7. show vpc brief

8. copy running-config startup-config

DETAILED STEPS

This example shows how to configure a vPC peer link:

Configuring the vPC Peer-Gateway

Beginning with Cisco NX-OS 4.2(1), you can configure vPC peer devices to act as the gateway for packets that are destined to the vPC peer device's MAC address.

Note When you attach a Layer 3 device to a vPC domain, the peering of routing protocols using a VLAN also carried on the vPC peer-link is not supported. If routing protocol adjacencies are needed between vPC peer devices and a generic Layer 3 device, you must use physical routed interfaces for the interconnection. Use of the vPC peer-gateway feature does not change this requirement.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. peer-gateway

4. exit

5. show vpc brief

6. copy running-config startup-config

DETAILED STEPS

Checking the Configuration Compatibility on a vPC Peer Link

After you have configured the vPC peer link on both vPC peer devices, check that the configurations are consistent on all vPC interfaces. See the “Compatibility Parameters for vPC Peer Links” section for information on consistent configurations on the vPCs.

SUMMARY STEPS

1. config t

2. show vpc consistency-parameters {global | interface port-channel channel-number}

DETAILED STEPS

This example shows how to check that the required configurations are compatible across all the vPC interfaces:

Note Messages regarding the vPC interface configuration compatibility are also logged to the syslog.

Moving Other Port Channels into a vPC

Note We recommend that you attach the vPC domain downstream port channel to two devices for redundancy.

To connect to the downstream device, you create a port channel from the downstream device to the primary vPC peer device and you create another port channel from the downstream device to the secondary peer device. Finally, working on each vPC peer device, you assign a vPC number to the port channel that connects to the downstream device. You will experience minimal traffic disruption when you are creating vPCs.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are using a Layer 2 port channel.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. interface port-channel channel-number

3. vpc number

4. exit

5. show vpc brief

6. copy running-config startup-config

DETAILED STEPS

This example shows how to configure a port channel that will connect to the downstream device:

Manually Configuring a vPC Domain MAC Address

When you create a vPC domain, the Cisco NX-OS software automatically creates a vPC system MAC address, which is used for operations that are confined to the link-scope, such as LACP. However, you may choose to configure the vPC domain MAC address manually.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. system-mac mac-address

4. exit

5. show vpc role

6. copy running-config startup-config

DETAILED STEPS

This example shows how to manually configure the vPC domain MAC address:

Manually Configuring the System Priority

When you create a vPC domain, the system automatically creates a vPC system priority. However, you can also manually configure a system priority for the vPC domain.

Note We recommend that you manually configure the vPC system priority when you are running LACP to ensure that the vPC peer devices are the primary devices on LACP. When you manually configure the system priority, ensure that you configure the same priority value on both vPC peer devices. If these values do not match, vPC will not come up.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. system-priority priority

4. exit

5. show vpc role

6. copy running-config startup-config

DETAILED STEPS

This example shows how to manually configure the vPC domain system priority:

Manually Configuring the vPC Peer Device Role

By default, the Cisco NX-OS software elects a primary and secondary vPC peer device after you configure the vPC domain and both sides of the vPC peer link. However, you may want to elect a specific vPC peer device as the primary device for the vPC. Then, you would manually configure the role value for the vPC peer device that you want as the primary device to be lower than the other vPC peer device.

vPC does not support role preemption. If the primary vPC peer device fails, the secondary vPC peer device takes over to become operationally the vPC primary device. However, the original operational roles are not restored if the formerly primary vPC comes up again.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. role priority priority

4. exit

5. show vpc role

6. copy running-config startup-config

DETAILED STEPS

This example shows how to manually configure the role priority of the vPC peer device:

Configuring the Tracking Feature on a Single-Module vPC

Beginning with Cisco NX-OS Release 4.2, if you must configure all the vPC peer links and core-facing interfaces on a single N7K-M132XP-12 module, you should configure a track object and a track list that is associated with the Layer 3 link to the core and on all the links on the vPC peer link on both primary vPC peer devices. Once you configure this feature and if the primary vPC peer device fails, the system automatically suspends all the vPC links on the primary vPC peer device. This action forces all the vPC traffic to the secondary vPC peer device until the system stabilizes.

You must put this configuration on both vPC peer devices. Additionally, you should put the identical configuration on both vPC peer devices because either device can become the operationally primary vPC peer device.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct virtual device context (VDC) (or use the switchto vdc command).

Ensure that you have configured the track object and the track list. Ensue that you assign all interfaces that connect to the core and to the vPC peer link to the track-list object on both vPC peer devices.

SUMMARY STEPS

1. config t

2. vpc domain domain-id

3. track track-object-id

4. exit

5. show vpc

6. copy running-config startup-config

DETAILED STEPS

This example shows how to put the previously configured track-list object into the vPC domain on the vPC peer device:

Configuring the vPC Peer Switch

You can configure the Cisco Nexus 7000 Series device to make a pair of vPC devices appear as a single STP root in the Layer 2 topology. This section includes the following topics:

• Configuring a Pure vPC Peer Switch Topology
• Configuring a Hybrid vPC Peer Switch Topology

Configuring a Pure vPC Peer Switch Topology

You can configure a pure vPC peer switch topology using the peer-switch command and then you set the best possible (lowest) spanning tree bridge priority value.

Note The values you apply for the spanning tree priority must be identical on both vPC peers.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vpc domain domain-id

3. peer-switch

4. spanning-tree vlan vlan-range priority value

5. exit

6. show spanning-tree summary

7. copy running-config startup-config

DETAILED STEPS

This example shows how to configure a pure vPC peer switch topology:

Configuring a Hybrid vPC Peer Switch Topology

You can configure a hybrid vPC and non-vPC peer switch topology by using the spanning-tree pseudo-information command (see the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Command Reference, Release 4.x .) to change the designated bridge ID so that it meets the STP VLAN-based load-balancing criteria and then change the root bridge ID priority to a value that is better than the best bridge priority. You then enable the peer switch.

Note If you previously configured global spanning tree parameters and you subsequently configure spanning tree pseudo information parameters, be aware that the pseudo information parameters take precedence over the global parameters.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. spanning-tree pseudo-information

3. vlan vlan-range designated priority value

4. vlan vlan-range root priority value

5. vpc domain domain-id

6. peer-switch

7. exit

8. show spanning-tree summary

9. copy running-config startup-config

DETAILED STEPS

This example shows how to configure a hybrid vPC peer switch topology:

Configuring Address Synchronization

The ip arp synchronize and ipv6 nd synchronize commands must be enabled and support faster convergence of address tables between the vPC peers.

vPC and IPv4 ARP Synchronization

You can disable or enable ARP synchronization between the vPC peers.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vpc domain domain-id

3. ip arp synchronize

4. exit

5. show ip arp sync-entries

6. show ip arp fhrp-non-active-learn

DETAILED STEPS

vPC and IPv6 ND Synchronization

You can disable or enable ND synchronization between the vPC peers.

BEFORE YOU BEGIN

Ensure that you have enabled the vPC feature.

Ensure that you are in the correct VDC (or use the switchto vdc command).

SUMMARY STEPS

1. configure terminal

2. vpc domain domain-id

3. ipv6 nd synchronize

4. exit

5. show ipv6 icmp sync-entries

6. show ipv6 icmp fhrp-non-active-learn

DETAILED STEPS

Related Documents

Standards

MIBs