A virtual port channel (vPC) allows links that are
physically connected to two different
Cisco Nexus 5000 Series
switches or
Cisco Nexus 2000 Series Fabric
Extenders
to appear as a single port channel by a third device (see the following
figure). The third device can be a switch, server, or any other networking
device. Beginning with
Cisco NX-OS
Release 4.1(3)N1(1), you can configure vPCs in topologies
that include
Cisco Nexus 5000 Series
switches connected to the
Fabric Extender.
A vPC can provide multipathing, which allows you to create redundancy by
enabling multiple parallel paths between
nodes and load balancing traffic where alternative paths exist.
Figure 1. vPC Architecture
You configure the EtherChannels by using one of the
following:
No
protocol
Link
Aggregation Control Protocol (LACP)
When you configure the EtherChannels in a
vPC—including the vPC peer link channel—each switch can have up to 16 active
links in a single EtherChannel. When you configure a vPC on a
Fabric Extender,
only one port is allowed in an EtherChannel.
Note
You must enable the vPC feature before you can
configure or run the vPC functionality.
To enable the vPC functionality, you must create a
peer-keepalive link under a vPC domain to send heartbeat messages between
the two vPC peer devices.
To create a vPC peer link you configure an
EtherChannel on one
Cisco Nexus 5000 Series
switch by using two or more Ethernet ports. On the other
switch, you configure another EtherChannel again using two or more Ethernet
ports. Connecting these two EtherChannels together creates a vPC peer link.
Note
We recommend that you configure the
vPC peer-link EtherChannels as trunks.
The vPC domain includes both vPC peer devices, the
vPC peer-keepalive link, the vPC peer link, and all of the EtherChannels in the
vPC domain connected to the downstream device. You can have only one vPC domain
ID on each vPC peer device.
Note
Always attach all vPC devices using
EtherChannels to both vPC peer devices.
A vPC provides the following benefits:
Allows
a single device to use an EtherChannel 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 switch fails
Provides link-level resiliency
Assures high availability
Terminology
vPC Terminology
The terminology used in vPCs is as follows:
vPC—The combined EtherChannel between the vPC
peer devices and the downstream device.
vPC peer device—One of a pair of devices that
are connected with the special EtherChannel known as the vPC peer link.
vPC peer link—The link used to synchronize
states between the vPC peer devices.
vPC member port—Interfaces that belong to the
vPCs.
Host vPC port—Fabric Extender
host interfaces that belong to a vPC.
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. The vPC domain ID must
be the same on both switches.
vPC peer-keepalive link—The peer-keepalive link
monitors the vitality of a vPC peer
Cisco Nexus 5000 Series
device. The peer-keepalive link sends configurable, periodic keepalive messages
between vPC peer devices.
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 vPCs.
Fabric Extender Terminology
The terminology used for the Cisco Nexus 2000 Series Fabric
Extender is as follows:
Fabric interface—A 10-Gigabit Ethernet uplink
port designated for connection from the Fabric Extender
to its parent switch. A fabric interface cannot be used for any other purpose.
It must be directly connected to the parent switch.
EtherChannel fabric interface—An EtherChannel
uplink connection from the
Fabric Extender to its parent switch. This connection consists of fabric interfaces bundled
into a single logical channel.
Host interface—An Ethernet interface for server
or host connectivity. These ports are 1-Gigabit Ethernet interfaces.
EtherChannel host interface—An EtherChannel
downlink connection from the
Fabric Extender host interface to a server port.
Note
In Release 4.1(3)N1(1), an EtherChannel host
interface consists of only one host interface and can be configured either as
a Link Aggregation Control Protocol (LACP) or non-LACP EtherChannel.
For further information about the Fabric Extender, refer to the Cisco Nexus 2000 Series Fabric Extender
Software Configuration Guide.
Supported vPC Topologies
Cisco Nexus 5000 Series Switch vPC Topology
You can connect a pair of
Cisco Nexus 5000 Series
switches configured in a vPC directly to another switch or to a server. Up to 8 interfaces could be connected to each Cisco Nexus 5000 Series switch providing 16 interfaces bundled for the vPC pair. The topology
that is shown in the following figure provides the vPC functionality to dual connected switches or servers with
10-Gigabit or 1-Gigabit Ethernet uplink interfaces.
Figure 2. Cisco Nexus 5000 Series Switch-to-Switch vPC Topology
Note
The first 8 ports on the
Cisco Nexus 5010
switch and the first 16 ports on the
Cisco Nexus 5020
switch are switchable 1-Gigabit and 10-Gigabit ports. You can enable vPC functionality on these ports in 1-Gigabit mode.
The switch connected to the pair of Cisco Nexus 5000 Series
switches can be any standards-based Ethernet switch. Common environments to use this configuration include Blade Chassis with dual switches connected to the pair of Cisco Nexus 5000 Series
switches through vPC or Unified Computing Systems connected to the pair of Cisco Nexus 5000 Series
switches.
Single Homed Fabric Extender vPC Topology
You can connect a server with dual interfaces that are configured in a vPC to a pair of
Cisco Nexus 2000 Series Fabric
Extenders
that you then connect single homed to the
Cisco Nexus 5000 Series
switches. The
topology that is shown in the following figure provides the vPC functionality to dual homed servers with
1-Gigabit Ethernet uplink interfaces.
Figure 3. Single Homed Fabric Extender vPC Topology
The
Cisco Nexus 5000 Series
switch can support up to 12 configured single homed Fabric Extenders (576 ports) with this
topology however only 480 dual homed host servers can be configured in a vPCs with this configuration.
Note
The current generation of Cisco Nexus 2000 Series Fabric
Extender does not support EtherChannels on its host interfaces. Therefore a maximum of two links can be configured in an EtherChannel from the server where each link is connected to a separate Fabric Extender.
Dual Homed Fabric Extender vPC Topology
You can connect the
Cisco Nexus 2000 Series Fabric
Extender
to two upstream
Cisco Nexus 5000 Series
switches and downstream to a number of single homed servers. The topology
shown in the following figure provides the vPC functionality to singly connected servers with 1-Gigabit
Ethernet uplink interfaces.
Figure 4.
Dual Homed Fabric Extender
vPC Topology
The
Cisco Nexus 5000 Series
switch can support up to 12 configured dual homed Fabric Extenders with this topology.
A maximum of 480 single homed servers can be connected to this configuration.
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 switches.
The vPC domain is a configuration mode that
you use to configure the keepalive messages and also configure other vPC peer link
parameters rather than accept the default values.
To create a vPC domain, you must first create a vPC
domain ID on each vPC peer switch using a number from 1 to 1000. This ID must
be the same on a set of vPC peer devices. Within this domain, the system
provides a loop-free topology and multipathing.
You can configure the EtherChannels and vPC peer
links by using LACP or no protocol. When possible, we recommend that you
use LACP with the interfaces in active mode to configure EtherChannels in each
vPC to ensure an optimized, graceful recovery in a port-channel failover
scenario and provides configuration checks against a configuration mismatch among
the EtherChannels.
The vPC peer switches 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 switches 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 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.
Note
You must set a unique vPC domain ID to
avoid system ID issues with LACP vPCs.
After you create a vPC domain, the
Cisco NX-OS
software automatically creates a system priority for the vPC domain. You can also manually configure a
specific system priority for the vPC domain.
Note
If you manually configure the system priority,
you must ensure that you assign the same priority value on both vPC peer
switches. If the vPC peer switches have different system priority values, the vPC
will not come up.
Peer-Keepalive Link and Messages
The
Cisco NX-OS
software uses a peer-keepalive link between the vPC peers to transmit
periodic, configurable keepalive messages. You must have Layer 3 connectivity
between the peer switches to transmit these messages; the system cannot bring
up the vPC peer link unless a peer-keepalive link is already up and running.
If one of the vPC peer switches fails, the vPC peer
switch on the other side of the vPC peer link senses the failure when it does not
receive any peer-keepalive messages. The default interval time for the vPC
peer-keepalive message is 1 second. You can configure the interval between
400 milliseconds and 10 seconds. You can also configure a timeout value with a
range of 3 to 20 seconds; the default timeout value is 5 seconds. The
peer-keepalive status is checked only when the peer-link goes down.
The vPC peer-keepalive can be carried either in the management or default VRF on the Cisco Nexus 5000 Series switch. When you configure the switches to use the management VRF, the source and destination for the keepalive messages are the mgmt 0 interface IP addresses. When you configure the switches to use the default VRF, an SVI must be created to act as the source and destination addresses for the vPC peer-keepalive messages. 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.
Note
We recommend that you configure the vPC peer-keepalive link on the Cisco Nexus 5000 Series switch to run in the management VRF using the mgmt 0 interfaces. If you configure the default VRF, ensure that the vPC peer link is not used to carry the vPC peer-keepalive messages.
Compatibility Parameters for vPC Peer Links
Many configuration and operational parameters must be identical on all
interfaces in the vPC. After you enable the vPC feature and configure the peer link on both
vPC peer switches, Cisco Fabric Services (CFS) messages provide a copy of the configuration on the
local vPC peer switch configuration to the remote vPC peer switch. The system
then determines whether any of the crucial configuration parameters differ on
the two switches.
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 EtherChannels.
The configuration parameters in this section must be configured
identically on both switches at either end of the vPC peer link or the vPC is moved into suspend
mode.
Note
You must ensure that all interfaces in the vPC have the identical
operational and configuration parameters listed in this section.
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 switch automatically check for compatibility 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 (MST)
Enable or disable state
per VLAN
STP global settings:
Bridge Assurance
setting
Port type setting—We
recommend that you set all vPC interfaces as network ports
Loop Guard settings
STP interface settings:
Port type setting
Loop Guard
Root Guard
Maximum Transmission Unit
(MTU)
Quality of Service global
settings
System QoS policy
System Network-QoS
policy
System Input Queuing
policy
System Output Queuing
policy
For the
Fabric Extender vPC topology, all the
interface level parameters mentioned above should be identically configured for
host interface from both the switches.
Fabric Extender FEX number configured on
an EtherChannel fabric interface; for the
Fabric Extender vPC toplogy.
If any of these parameters are not enabled or defined on either
switch, 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 switches, a misconfiguration may cause undesirable behavior in
the traffic flow:
MAC aging timers
Static MAC entries
VLAN interface—Each switch
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 switch 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 switches, or the VLAN will be suspended.
Private VLAN configuration
All ACL configurations and
parameters
Quality of service (QoS)
configuration and parameters—Local parameters; global parameters must be
identical
STP interface settings:
BPDU Filter
BPDU Guard
Cost
Link type
Priority
VLANs (Rapid PVST+)
To ensure that all the configuration parameters are compatible, we
recommend that you display the configurations for each vPC peer switch once you
configure the vPC.
vPC Peer Links
A vPC peer link is the link that is used to
synchronize the states between the vPC peer devices.
Note
You must configure the peer-keepalive link
before you configure the vPC peer link or the peer link will not come up.
You can have only two switches as vPC peers; each
switch can serve as a vPC peer to only one other vPC peer. The vPC peer
switches can also have non-vPC links to other switches.
To make a valid configuration, you configure
an EtherChannel on each switch and then configure the vPC domain. You assign
the EtherChannel on each switch as a peer link. For redundancy, we recommend
that you should configure at least two dedicated ports into the
EtherChannel; if one of the interfaces in the vPC peer link fails, the
switch automatically falls back to use another interface in the peer link.
Note
We recommend that you configure the
EtherChannels in trunk mode.
Many operational parameters and configuration
parameters must be the same in each switch connected by a vPC peer link.
Because each switch is completely independent on the management plane, you must
ensure that the switches are compatible on the critical parameters. vPC peer
switches have separate control planes. After configuring the vPC peer link, you
should display the configuration on each vPC peer switch to ensure that the
configurations are compatible.
Note
You must ensure that the two switches connected
by the vPC peer link have certain identical operational and configuration
parameters.
When you configure the vPC peer link, the vPC peer
switches negotiate that one of the connected switches is the primary switch and
the other connected switch is the secondary switch. By default, the
Cisco NX-OS
software uses the lowest MAC address to elect the primary switch. The software
takes different actions on each switch—that is, the primary and secondary—only
in certain failover conditions. If the primary switch fails, the secondary
switch becomes the operational primary switch when the system recovers, and the
previously primary switch is now the secondary switch.
You can also configure which of the vPC switches is
the primary switch. If you want to configure the role priority again to make
one vPC switch the primary switch, configure the role priority on both the
primary and secondary vPC switches with the appropriate values, shut down
the EtherChannel that is the vPC peer link on both switches by entering the
shutdown
command, and reenable the EtherChannel on both switches by entering
the
no shutdown
command.
For known unicast traffic, you should use the local links of the
vPC because you cannot load balance traffic across the peer link. Unknown
unicast, multicast, and broadcast traffic are flooded across the vPC peer link.
The software keeps the multicast forwarding state synchronized between the two
peers for groups learned over the vPC link. If the multicast forwarding states
are learned over isolated ports on either peer, the states are not synchronized, but
since the peer link is a router port, the traffic is forwarded to the peer; the
peer then handles the forwarding if there are other isolated ports on that
switch.
MAC addresses that are learned over vPC links are also synchronized
between the peers.
Configuration information flows across the vPC peer
links using the Cisco Fabric Services over Ethernet (CFSoE) protocol. All MAC
addresses for those VLANs configured on both switches are synchronized between
vPC peer switches. The software uses CFSoE for this synchronization.
If the vPC peer link fails, the software checks the
status of the remote vPC peer switch using the peer-keepalive link, which is a
link between vPC peer switches, to ensure that both switches are up. If the
vPC peer switch is up, the secondary vPC switch disables all vPC ports on its
switch to prevent loops and disappearing or flooding traffic. The data
then forwards down the remaining active links of the EtherChannel.
The software learns of a vPC peer switch 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 switches. 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 switch. The keepalive messages
are used only when all the links in the peer link fail.
Manually Configured vPC Features
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 highest STP root priority, and configure the secondary device with a
lower root priority.
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.
We recommend that you configure Unidirectional
Link Detection (UDLD) on both sides of the vPC peer link.
vPC Number
Once you have created the vPC domain ID and the vPC peer link, you
can create EtherChannels to attach the downstream switch to each vPC peer switch.
That is, you create one EtherChannel from the downstream switch to the primary
vPC peer switch and you create another EtherChannel from the downstream switch
to the secondary peer switch.
On each vPC peer switch, you assign the same vPC number to the
EtherChannel that connects to the downstream switch. You will experience
minimal traffic disruption when you are creating vPCs. To simplify the
configuration, you can assign the vPC ID number for each EtherChannel to be the
same as the EtherChannel itself (that is, vPC ID 10 for EtherChannel 10).
Note
The vPC number that you assign to the EtherChannel connecting to
the downstream switch from the vPC peer switch must be identical on both vPC
peer switches.
vPC Interactions with Other Features
vPC and LACP
The Link Aggregation Control Protocol (LACP) uses the system MAC address of the vPC domain to form the LACP
Aggregation Group (LAG) ID for the vPC.
You can use LACP on all the vPC EtherChannels, including those
channels from the downstream switch. We recommend that you configure LACP with
active mode on the interfaces on each EtherChannel on the vPC peer switches.
This configuration allows you to more easily detect compatibility between
switches, unidirectional links, and multihop connections, and provides dynamic
reaction to run-time changes and link failures.
The vPC peer link supports 16 EtherChannel LACP interfaces. You should manually configure the system priority on the vPC peer-link
switches to ensure that the vPC peer-link switches have a higher LACP priority
than the downstream connected switches. 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 switches. If the vPC peer
switches have different system priority values, vPC will not come up.
vPC Peer Links and STP
When you first bring up the vPC functionality, 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.
You must configure a list of parameters to be identical on the vPC
peer switches on both sides of the vPC peer link.
STP is distributed; that is, the protocol continues running on both
vPC peer switches. However, the configuration on the vPC peer switch elected as
the primary switch controls the STP process for the vPC interfaces on the
secondary vPC peer switch.
The primary vPC switch synchronizes the STP state on the vPC secondary
peer switch using Cisco Fabric Services over Ethernet (CFSoE).
The vPC manager performs a proposal/handshake agreement between the
vPC peer switches that sets the primary and secondary switches and coordinates
the two switches for STP. The primary vPC peer switch then controls the STP
protocol for vPC interfaces on both the primary and secondary switches. We
recommend that you configure the primary vPC peer switch as the highest STP
root priority, and configure the secondary switch with a lower root priority.
If the primary vPC peer switch fails over to the secondary vPC peer
switch, there is no change in the STP topology.
The Bridge Protocol Data Units (BPDUs) use the MAC address set for the vPC for the STP bridge ID in
the designated bridge ID field. The vPC primary switch sends these BPDUs on the
vPC interfaces.
Note
Display the configuration on both sides of the vPC peer link to
ensure that the settings are identical.
Use the
show spanning-tree command to display information
about the vPC.
CFSoE
The Cisco Fabric Services over Ethernet (CFSoE) is a reliable state
transport mechanism that you can use 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 do not need
to configure anything for the CFSoE feature to work correctly on vPCs.
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. CFSoE
must be enabled for vPC functionality. If you do enter either of these commands when vPC
is 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.
vPC Guidelines and Limitations
vPC has the following configuration guidelines and limitations:
You must enable the vPC
feature before you can configure vPC peer-link and vPC interfaces.
You must configure the
peer-keepalive link before the system can form the vPC peer link.
Only EtherChannels can be
in vPCs. A vPC can be configured on a normal EtherChannel (switch-to-switch vPC
topology), on an EtherChannel fabric interface (fabric extender vPC topology),
and on an EtherChannel host interface (host interface vPC topology).
Note
Refer to the Cisco Nexus 2000 Series Fabric Extender
Software Configuration Guide for
information about Fabric Extender host and fabric interfaces.
A Fabric Extender can be a member of a Host Interface vPC topology or a Fabric Extender vPC topology but not both simultaneously.
You must configure both
vPC peer switches; the configuration is not automatically synchronized between
the vPC peer devices.
Check that the necessary
configuration parameters are compatible on both sides of the vPC peer link.
You may experience minimal
traffic disruption while configuring vPCs.
You
should configure all the EtherChannels in the vPC using LACP with the interfaces in
active mode.
Configuring vPCs
Enabling vPCs
You must enable the vPC feature before you can configure and use
vPCs.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
feature vpc
Enables vPCs on the switch.
Step 3
switch#
show feature
(Optional)
Displays which features are enabled on the switch.
Step 4
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to enable the vPC feature:
switch# configure terminal
switch(config)# feature vpc
Disabling vPCs
You can disable the vPC feature.
Note
When you disable the vPC feature, the Cisco Nexus 5000 Series switch clears all the vPC
configurations.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
no feature vpc
Disables vPCs on the switch.
Step 3
switch#
show feature
(Optional)
Displays which features are enabled on the switch.
Step 4
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to disable the vPC feature:
switch# configure terminal
switch(config)# no feature vpc
Creating a vPC Domain
You must create identical vPC domain IDs on both the vPC peer devices.
This domain ID is used to automatically form the vPC system MAC address.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
vpc domaindomain-id
Creates a vPC domain on the switch, and enters the vpc-domain
configuration mode. There is no default
domain-id; the range is from 1 to 1000.
Note
You can also use the
vpc domain command to enter the vpc-domain
configuration mode for an existing vPC domain.
Step 3
switch#
show vpc brief
(Optional)
Displays brief information about each vPC domain.
Step 4
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to create a vPC domain:
switch# configure terminal
switch(config)# vpc domain 5
Configuring a vPC Keepalive 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.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure the vPC peer-keepalive link before the system can
form the vPC peer link.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
vpc domaindomain-id
Creates a vPC domain on the switch if it does not already exist,
and enters the vpc-domain configuration mode.
You can create a vPC peer link by designating the EtherChannel that you
want on each switch as the peer link for the specified vPC domain. We recommend
that you configure the EtherChannels 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 switch for redundancy.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedures
To connect to a downstream server from a
Cisco Nexus 2000 Series Fabric
Extender you can create a
EtherChannel host interface.
An EtherChannel host interface can have only one host interface as a
member. You need to create an EtherChannel host interface to configure a vPC on it
that uses the
Fabric Extender topology.
Note
See the Cisco Nexus 2000 Series Fabric Extender
Software Configuration Guide for
information on attaching a Fabric Extender to a Cisco Nexus 5000 Series switch.
Before You Begin
Ensure that you have enabled the vPC feature.
Ensure that the connected
Fabric Extender is online.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Creates an EtherChannel host interface on the selected host
interface.
Step 4
switch#
show port-channel summary
(Optional)
Displays information about each EtherChannel host interface.
Step 5
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to configure an EtherChannel host interface:
switch# configure terminal
switch(config)# interface ethernet 101/1/20
switch(config-if)# channel-group 7 mode active
Moving Other EtherChannels into a vPC
To connect to the downstream switch, you create a EtherChannel from
the downstream switch to the primary vPC peer switch and you create another
EtherChannel from the downstream switch to the secondary peer switch. Finally,
working on each vPC peer switch, you assign a vPC number to the EtherChannel
that connects to the downstream switch. You will experience minimal traffic
disruption when you are creating vPCs.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Selects the EtherChannel that you want to put into the vPC to
connect to the downstream switch, and enters the interface configuration mode.
Note
A vPC can be configured on a normal EtherChannel (physical vPC
topology), on an EtherChannel fabric interface (fabric extender vPC topology),
and on an EtherChannel host interface (host interface vPC topology)
Step 3
switch(config-if)#
vpcnumber
Configures the selected EtherChannel into the vPC to connect to
the downstream switch. The range is from 1 to 4096.
The vPC
number that you assign to the
EtherChannel connecting to the downstream switch from the vPC peer switch must
be identical on both vPC peer switches.
Step 4
switch#
show vpc brief
(Optional)
Displays information about each vPC.
Step 5
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to configure an EtherChannel that will connect
to the downstream device:
switch# configure terminal
switch(config)# interface port-channel 20
switch(config-if)# vpc 5
Manually Configuring a vPC Domain MAC Address
You create the vPC peer link by designating the EtherChannel that you
want on each switch as the peer link for the specified vPC domain. We recommend
that you configure the EtherChannels 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 switch for redundancy.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
vpc domaindomain-id
Selects an existing vPC domain on the switch, or creates a new vPC
domain, and enters the vpc-domain configuration mode. There is no default
domain-id; the range is from 1 to 1000.
Step 3
switch(config-vpc-domain)#
system-macmac-address
Enters the MAC address that you want for the specified vPC domain
in the following format: aaaa.bbbb.cccc.
Step 4
switch#
show vpc role
(Optional)
Displays the vPC system MAC address.
Step 5
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to configure a vPC domain MAC address:
switch# configure terminal
switch(config)# vpc domain 5
switch(config-if)# system-mac 23fb.4ab5.4c4e
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 switches are the primary
switches on LACP. When you manually configure the system priority, ensure that
you configure the same priority value on both vPC peer switches. If these
values do not match, vPC will not come up.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
vpc domaindomain-id
Selects an existing vPC domain on the switch, or creates a new vPC
domain, and enters the vpc-domain configuration mode. There is no default
domain-id; the range is from 1 to 1000.
Enters the system priority that you want for the specified vPC
domain. The range of values is from 1 to 65535. The default value is 32667.
Step 4
switch#
show vpc brief
(Optional)
Displays information about each vPC, including information about
the vPC peer link.
Step 5
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to configure a vPC peer link:
switch# configure terminal
switch(config)# vpc domain 5
switch(config-if)# system-priority 4000
Manually Configuring a vPC Peer Switch Role
By default, the
Cisco NX-OS software elects a
primary and secondary vPC peer switch after you configure the vPC domain and
both sides of the vPC peer link. However, you may want to elect a specific vPC
peer switch as the primary switch for the vPC. Then, you would manually
configure the role value for the vPC peer switch that you want as the primary
switch to be lower than the other vPC peer switch.
vPC does not support role preemption. If the primary vPC peer switch
fails, the secondary vPC peer switch takes over to become operationally the vPC
primary switch. However, the original operational roles are not restored when the
formerly primary vPC comes up again.
Before You Begin
Ensure that you have enabled the vPC feature.
You must configure both switches on either side of the vPC
peer link with the following procedure.
Procedure
Command or Action
Purpose
Step 1
switch#
configure terminal
Enters configuration mode.
Step 2
switch(config)#
vpc domaindomain-id
Selects an existing vPC domain on the switch, or creates a new vPC
domain, and enters the vpc-domain configuration mode. There is no default
domain-id; the range is from 1 to 1000.
Step 3
switch(config-vpc-domain)#
role prioritypriority
Enters the role priority that you want for the vPC system
priority. The range of values is from 1 to 65535. The default value is 32667.
Step 4
switch#
show vpc brief
(Optional)
Displays information about each vPC, including information about
the vPC peer link.
Step 5
switch#
copy running-config startup-config
(Optional)
Copies the running configuration to the startup configuration.
This example shows how to configure a vPC peer link:
switch# configure terminal
switch(config)# vpc domain 5
switch(config-if)# role priority 4000
Verifying the vPC Configuration
Use the following commands to display vPC configuration information:
Command
Purpose
switch# show feature
Displays whether vPC is enabled or not.
switch# show port-channel capacity
Displays how many EtherChannels are configured and how many are still available on the switch.
switch# show running-config vpc
Displays running configuration information for vPCs.
switch# show vpc brief
Displays brief information on the vPCs.
switch# show vpc consistency-parameters
Displays the status of those parameters that must be consistent across all vPC interfaces.
switch# show vpc peer-keepalive
Displays information on the peer-keepalive messages.
switch# show vpc role
Displays the peer status, the role of the local switch, the vPC system MAC address and system priority, and the MAC address and priority for the local vPC switch.
switch# show vpc statistics
Displays statistics on the vPCs.
Note
This command displays the vPC statistics only for the vPC peer device that you are working on.
For detailed information about the fields in the output from these commands, see the Cisco Nexus 5000 Series Command
Reference.
vPC Example Configurations
Dual Homed Fabric Extender vPC Configuration Example
The following example shows how to configure the dual homed Fabric Extender vPC topology using the management VRF to carry the peer-keepalive messages on switch NX-5000-1 as
shown in following figure:
Figure 5. vPC Configuration Example
Before You Begin
Ensure that the Cisco Nexus 2000 Series Fabric
Extender NX-2000-100 is attached and online.
Procedure
Step 1
Enable vPC and LACP.
NX-5000-1# configure terminal
NX-5000-1(config)# feature lacp
NX-5000-1(config)# feature vpc
Step 2
Create the vPC domain and add the vPC peer-keepalive link.
Single Homed Fabric Extender vPC Configuration Example
The following example shows how to configure the single homed Fabric Extender vPC topology using the default VRF to carry the peer-keepalive messages on switch NX-5000-1 as
shown in following figure:
Figure 6. vPC Configuration Example
Note
The following example only shows the configuration of NX-5000-1 which is connected to the Fabric Extender NX-2000-100. You must repeat these steps on its vPC peer, NX-5000-2, which is connected to the Fabric Extender NX-2000-101.
Before You Begin
Ensure that the Cisco Nexus 2000 Series Fabric
Extenders NX-2000-100 and NX-2000-101 are attached and online.
Procedure
Step 1
Enable vPC and LACP.
NX-5000-1# configure terminal
NX-5000-1(config)# feature lacp
NX-5000-1(config)# feature vpc
Step 2
Enable SVI interfaces, create the VLAN and SVI to be used by the vPC peer-keepalive link.
NX-5000-1(config)# feature interface-vlan
NX-5000-1(config)# vlan 900
NX-5000-1(config-vlan)# int vlan 900
NX-5000-1(config-if)# ip address 10.10.10.236 255.255.255.0
NX-5000-1(config-if)# no shutdown
NX-5000-1(config-if)# exit
Step 3
Create the vPC domain and add the vPC peer-keepalive link in the default VRF.
VLAN 900 must not be trunked across the vPC peer-link because it carries the vPC peer-keepalive messages. There must be an alternative path between switches NX-5000-1 and NX-5000-2 for the vPC peer-keepalive messages.
Step 4
Configure the vPC peer link as a two port Etherchannel.