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Restrictions for Cisco StackWise Virtual
The Federal Information Processing Standards (FIPS) is not supported on Cisco StackWise Virtual links.
In Cisco IOS XE Denali 16.3.3, the maximum number of Cisco StackWise Virtual links supported is four.
In Cisco IOS XE Denali 16.6.x, the maximum number of Cisco StackWise Virtual links supported is eight.
Cisco StackWise Virtual is supported only on the following Cisco Catalyst 3850 Series Switch models.
Release
Supported switch models
16.3.x
WS-C3850-48XS-S
WS-C3850-48XS-E
WS-C3850-48XS-F-S
WS-C3850-48XS-F-E
16.6.x
WS-C3850-48XS-S
WS-C3850-48XS-E
WS-C3850-48XS-F-S
WS-C3850-48XS-F-E
The dual active and StackWise Virtual link configuration are performed dynamically and the device should be rebooted after
configuration.
The uplink ports on the switch do not support Dual-Active Detection.
Cisco StackWise Virtual is supported in IP services and IP base licenses.The licenses must be matched between two Cisco StackWise
Virtual member switches. License migration requires both Cisco StackWise Virtual member switches to be rebooted to activate
the licenses.
When deploying StackWise Virtual, ensure that VLAN ID 4094 is not used anywhere on the network. All inter-chassis system control
communication between stack members is carried over the reserved VLAN ID 4094 from the global range.
Prerequisites for Cisco StackWise Virtual
All the switches in Cisco StackWise Virtual solution must be of the same switch model.
All the switches in Cisco StackWise Virtual solution must be running the same license level.
All the switches in Cisco StackWise Virtual must be running the same software version.
Information About Cisco Stackwise Virtual
StackWise Virtual Overview
Cisco StackWise Virtual is a network system virtualization technology that pairs two switches into one virtual switch. Switches
in a Cisco StackWise Virtual solution simplify operational efficiency with a single control and management plane, scale system
bandwidth with distributed forwarding plane, and assist in building resilient networks using the recommended network design.
Cisco StackWise Virtual allows two physical switches to operate as a single logical virtual switch using a 40G or 10G Ethernet
connection.
Cisco StackWise Virtual Topology
A typical network design consists of core, distribution, and access layers. The default mode of a switch is standalone. When
two redundant switches are deployed in the distribution layer, the following network challenges arise:
If VLAN IDs are reused between access layers then, it will introduce a spanning tree loop that will impact the overall performance
of the network.
Spanning tree protcols and configuration are required to protect Layer 2 network against spanning tree protcol loop, and root
and bridge protocol data unit management.
Additional protocols such as first hop redundancy protocol are required to virtualize the IP gateway function. This should
align with STP root priorities for each VLAN.
The Protocol independent multicast designated router (PIM DR) configuration should be fine-tuned to selectively build a multicast
forwarding topology on a VLAN.
The standalone distribution layer system provides protocol-driven remote failure and detection, which results in slower convergence
time. Fine-tune FHRP and PIM timers for rapid fault detection and recovery process.
We recommend the Cisco StackWise Virtual model for aggregation layers and collapsed aggregation and core layers. The stack
can be formed over a redundant 40G or 10G fiber links to ensure that the distribution or the aggregation switches can be deployed
over a large distance.
Note that STP keeps one of the ports connected to the distribution switches blocked on the access switches. As a result of
this, an active link failure causes STP convergence and the network suffers from traffic loss, flooding, and a possible transient
loop in the network. On the other hand, if the switches are logically merged into one switch, all the access switches might
form an EtherChannel bundle with distribution switches, and a link failure within an EtherChannel would not have any impact
as long as at least one member within the EtherChannel is active.
Figure 1. Typical Network Design using Cisco StackWise Virtual
Etherchannel in StackWise Virtual is capable of implementing MEC across the stack members. When access layer and aggregation
layer are collapsed into a single StackWise Virtual system, MEC across the different access layer domain members and across
distribution and access layer switches will not be supported. MEC is designed to forward the traffic over the local link irrespective
of the hash result.
Since the control plane, management plane, and data plane are integrated, the system behaves as a single switch.
The virtualization of multiple physical switches into a single logical switch is from a control and management plane perspective
only. Because of the control plane being common, it may look like a single logical entity to peer switches. The data plane
of the switches are distributed. Each switch is capable of forwarding over its local interfaces without involving other members.
However, when a packet coming into a switch has to be forwarded over a different member’s port, the forwarding context of
the packet is carried over to the destination switch after ingress processing is performed in the ingress switch. Egress processing
is done only in the egress switch. This provides a uniform data plane behavior to the entire switch irrespective whether of
the destination port is in a local switch or in a remote switch. However, the common control plane ensures that all the switches
have equivalent data plane entry for each forwarding entity.
An election mechanism elects one of the switches to be Cisco StackWise Virtual active and the other switch to be Cisco StackWise
Virtual standby in terms of Control Plane functions. The active switch is responsible for all the management, bridging and
routing protocols, and software data path. The standby switch is in hot standby state ready to take over the role of active,
if the active switch fails over.
The following are the components of the Cisco StackWise Virtual solution:
Stack members
StackWise Virtual link: 10G or 40G Ethernet connections
StackWise Virtual link is the link that connects the switches over Ethernet. Typically, Cisco StackWise Virtual consits of
multiple 10G or 40G physical links. It carries all the control and data traffic between the switching units. You can configure
a StackWise Virtual link on any supported port. When a switch is powered up and the hardware is initiliazed, it looks for
a configured StackWise Virtual link before the initilization of the control plane.
The Link Management Protocol (LMP) is activated on each link of the StackWise Virtual links as soon as the links are established.
LMP ensure the integrity of SVL links and monitors and maintains the health of the links. The redundancy role of each switch
is resolved by the StackWise Discovery Protocol (SDP). It ensures that the hardware and software versions are compatible to
form the SVL and determines which switch becomes active or standby from a control plane perspective.
Cisco StackWise Virtual Header (SVH) is 64-byte overhead frame that is appended over all control, data, and management plane
traffic that traverse over each SVL between the two stack members of the Cisco StackWise Virtual domain. The SVH-encapsulated
traffic operates at OSI Layer 2 and can be recognized and processed only by Cisco StackWise Virtual-enabled switches. SVL
interfaces are nonbridgeable, and allows nonrouteable traffic over a L2 or L3 network.
Cisco StackWise Virtual Redundancy
Cisco StackWise Virtual operates stateful switchover (SSO) between the active and standby switches. The following are the
ways in which Cisco StackWise Virtual's redundancy model differs from that of the standalone mode:
The Cisco StackWise Virtual active and standby switches are hosted in separate switches and use a StackWise Virtual link to
exchange information.
The active switch controls both the switches of Cisco StackWise Virtual. The active switch runs the Layer 2 and Layer 3 control
protocols and manages the switching modules of both the switches.
The Cisco StackWise Virtual active and standby switches perform data traffic forwarding.
Note
If the Cisco StackWise Virtual active switch fails, the standby switch initiates a switchover and assumes the Cisco StackWise
Virtual active switch role.
SSO Redundancy
A StackWise Virtual system operates with SSO redundancy if it meets the following requirements:
Both the switches must be running the same software version, unless they are in the process of software upgrade.
StackWise Virtual link-related configuration in the two switches must match.
License type must be same on both the switch models.
Both the switch models must be in the same StackWise Virtual domain.
With SSO redundancy, the StackWise Virtual standby switch is always ready to assume control if a fault occurs on the StackWise
Virtual active switch. Configuration, forwarding, and state information are synchronized from the StackWise Virtual active
switch to the redundant switch at startup, and whenever changes to the StackWise Virtual active switch configuration occur.
If a switchover occurs, traffic disruption is minimized.
If StackWise Virtual does not meet the requirements for SSO redundancy, it will be incapable of establishing a relationship
with the peer switch. StackWise Virtual runs stateful switchover (SSO) between the StackWise Virtual active and standby switches.
The StackWise Virtual determines the role of each switch during initialization.
The CPU in the StackWise Virtual standby switch runs in hot standby state. StackWise Virtual uses a StackWise Virtual link
to synchronize configuration data from the StackWise Virtual active switch to the StackWise Virtual standby switch. Also,
protocols and features that support high availability synchronize their events and state information to the StackWise Virtual
standby switch.
Nonstop Forwarding
While implementing Nonstop Forwarding (NSF) technology in systems using SSO redundancy mode, network disruptions are transparent
to campus users and applications. High availability is provided even when the control-plane processing stack-member switch
is reset. During a failure of the underlying Layer 3, NSF-capable protocols perform graceful network topology resynchronization.
The preset forwarding information on the redundant stack-member switch remains intact; this switch continues to forward the
data in the network. This service availability significantly lowers the mean time to repair (MTTR) and increases the mean
time between failure (MTBF) to achieve a high level of network availability.
Multichassis EtherChannels
A Multichassis EtherChannel (MEC) is an EtherChannel bundled with physical ports having common characteristics such as speed
and duplex, that are distributed across each Cisco StackWise Virtual system. A Cisco StackWise Virtual MEC can connect to
any network element that supports EtherChannel (such as a host, server, router, or switch). Cisco StackWise Virtual supports
up to 128 MECs deployed in Layer 2 or Layer 3 modes. EtherChannel 128 is reserved for SVL connections. Hence, the maximum
available MEC count is 127.
In a Cisco StackWise Virtual system, an MEC is an EtherChannel with additional capability. A multichassis EtherChannel link
reduces the amount of traffic that requires transmission across the StackWise Virtual link by populating the index port only
with the ports local to the physical switch. This allows the switch to give precedence to the local ports of the multichassis
EtherChannel link over those on the remote switch.
Each MEC can optionally be configured to support either Cisco PAgP, IEEE LACP, or Static ON mode. We recommend that you implement
EtherChannel using Cisco PAgP or LACP with a compatible neighbor. If a remotely connected neighbor such as Cisco Wireless
LAN Controller (WLC) does not support this link-bundling protocol, then a Static ON mode can be deployed. These protocols
run only on the Cisco StackWise Virtual active switch.
An MEC can support up to eight physical links that can be distributed in any proportion between the Cisco StackWise Virtual
active switch and the Cisco StackWise Virtual standby switch. We recommend that you distribute the MEC ports across both switches
evenly.
MEC Minimum Latency Load Balancing
The StackWise Virtual environment is designed such that data forwarding always remains within the switch. The Virtual Stack
always tries to forward traffic on the locally available links. This is true for both Layer 2 and Layer3 links. The primary
motivation for local forwarding is to avoid unnecessarily sending data traffic over the StackWise Virtual link and thus reduce
the latency (extra hop over the SVL) and congestion.The bidirectional traffic is load-shared between the two StackWise Virtual
members. However, for each StackWise Virtual member, ingress and egress traffic forwarding is based on locally-attached links
that are part of MEC. This local forwarding is a key concept in understanding convergence and fault conditions in a StackWise
Virtual enabled campus network.
The active and standby switches support local forwarding that will individually perform the desired lookups and forward the
traffic on local links to uplink neighbors. If the destination is a remote switch in the StackWise Virtual domain, ingress
processing is performed on the ingress switch and then traffic is forwarded over the StackWise Virtual link to the egress
switch where only egress processing is performed.
Note
Minimum Latency Load Balancing is not supported in Cisco IOS XE Denali 16.3.3.
MEC Failure
Scenarios
We recommend that you configure a MEC with at least one link to each switch. This configuration ensures that there is always
an alternate path for data traffic in case of a switch failure.
The following sections describe issues that may arise and the resulting impact:
Single MEC Link
Failure
If a link within a MEC fails (and other links in the MEC are still operational), the MEC redistributes the load among the
operational links, as in a regular port.
All MEC Links to the Cisco StackWise Virtual Active Switch Fail
If all the links to the Cisco StackWise Virtual active switch fail, a MEC becomes a regular EtherChannel with operational
links to the Cisco StackWise Virtual standby switch.
Data traffic that terminates on the Cisco StackWise Virtual active switch reaches the MEC by crossing a StackWise Virtual
link to the Cisco StackWise Virtual standby switch. Control protocols continue to run in the Cisco StackWise Virtual active
switch. Protocol messages reach the MEC by crossing a StackWise Virtual link.
All MEC Links
Fail
If all the links in an MEC fail, the logical interface for the EtherChannel is set to Unavailable. Layer 2 control protocols
perform the same corrective action as for a link-down event on a regular EtherChannel.
On adjacent switches, routing protocols and the Spanning Tree Protocol (STP) perform the same corrective action as for a
regular EtherChannel.
Cisco StackWise Virtual Standby Switch Failure
If the Cisco StackWise Virtual standby switch fails, a MEC becomes a regular EtherChannel with operational links on the Cisco
StackWise Virtual active switch. Connected peer switches detect the link failures, and adjust their load-balancing algorithms
to use only the links to the StackwWise Virtual active switch.
Cisco StackWise Virtual Active Switch Failure
Cisco StackWise Virtual active switch failure results in a stateful switchover (SSO). After the switchover, a MEC is operational
on the new Cisco StackWise Virtual active switch. Connected peer switches detect the link failures (to the failed switch),
and adjust their load-balancing algorithms to use only the links to the new Cisco StackWise Virtual active switch.
Cisco StackWise Virtual Packet Handling
In Cisco StackWise Virtual, the Cisco StackWise Virtual active switch runs the Layer 2 and Layer 3 protocols and features
and manages the ports on both the switches.
Cisco StackWise Virtual uses StackWise Virtual link to communicate system and protocol information between the peer switches
and to carry data traffic between the two switches.
The following sections describe packet handling in Cisco StackWise Virtual.
Traffic on a StackWise Virtual link
A StackWise Virtual link carries data traffic and in-band control traffic between two switches. All the frames that are forwarded
over the StackWise Virtual link are encapsulated with a special StackWise Virtual Header (SVH). The SVH adds an overhead of
64 bytes for control and data traffic, which provides information for Cisco StackWise Virtual to forward the packet on the
peer switch.
A StackWise Virtual link transports control messages between two switches. Messages include protocol messages that are processed
by the Cisco StackWise Virtual active switch, but received or transmitted by interfaces on the Cisco StackWise Virtual standby
switch. Control traffic also includes module programming between the Cisco StackWise Virtual active switch and the switching
modules on the Cisco StackWise Virtual standby switch.
Cisco StackWise Virtual transmits data traffic over a StackWise Virtual link under the following circumstances:
Layer 2 traffic
flooded over a VLAN (even for dual-homed links).
Packets processed by software on the Cisco StackWise Virtual active switch where the ingress interface is on the Cisco StackWise
Virtual standby switch.
The packet destination is on the peer switch, as described in the following examples:
Traffic within a VLAN where the known destination interface is on the peer switch.
Traffic that is replicated for a multicast group and the multicast receivers are on the peer switch.
The known unicast destination MAC address is on the peer switch.
The packet is a MAC notification frame destined for a port on the peer switch.
A StackWise Virtual link also transports system data, such as NetFlow export data and SNMP data, from the Cisco StackWise
Virtual standby switch to the Cisco StackWise Virtual active switch.
Traffic on the StackWise Virtual link is load balanced with the same global hashing algorithms available for EtherChannels
(the default algorithm is source-destination IP).
Layer 2
Protocols
The Cisco StackWise Virtual active switch runs the Layer 2 protocols (such as STP and VTP) for the switching modules on both
the switches. Protocol messages that are transmitted and received on the Cisco StackWise Virtual standby switch switching
modules must traverse a StackWise Virtual link to reach the Cisco StackWise Virtual active switch.
All the Layer 2 protocols in Cisco StackWise Virtual work similarly in standalone mode. The following sections describe the
difference in behavior for some protocols in Cisco StackWise Virtual.
Spanning Tree Protocol
The Cisco StackWise Virtual active switch runs the STP. The Cisco StackWise Virtual standby switch redirects the STP BPDUs
across a StackWise Virtual link to the Stackwise Virtual active switch.
The STP bridge ID is commonly derived from the switch MAC address. To ensure that the bridge ID does not change after a switchover,
Cisco StackWise Virtual continues to use the original switch MAC address for the STP Bridge ID.
EtherChannel
Control Protocols
Link Aggregation Control Protocol (LACP) and Port Aggregation Protocol (PAgP) packets contain a device identifier. Cisco
StackWise Virtual defines a common device identifier for both the switches. Use either PAgP or LACP on Multi EtherChannels
instead of mode ON, even if all the three modes are supported.
Note
A new PAgP enhancement has been defined for assisting with dual-active scenario detection.
Switched Port Analyzer
Switched Port Analyzer (SPAN) on StackWise Virtual link ports is not supported; SVL ports can be neither a SPAN source, nor
a SPAN destination. Cisco StackWise Virtual supports all the SPAN features for non-SVL interfaces. The number of SPAN sessions
that are available on Cisco StackWise Virtual matches that on a single switch running in standalone mode.
Private
VLANs
Private VLANs on Stackwise Virtual work the same way as in standalone mode. The only exception is that the native VLAN on
isolated trunk ports must be configured explicitly.
Apart from STP, EtherChannel Control Protocols, SPAN, and private VLANs, the Dynamic Trunking Protocol (DTP), Cisco Discovery
Protocol (CDP), VLAN Trunk Protocol (VTP), and Unidirectional Link Detection Protocol (UDLD) are the additional Layer 2 control-plane
protocols that run over the SVL connections.
Layer 3
Protocols
The Cisco StackWise Virtual active switch runs the Layer 3 protocols and features for the Stackwise Virtual. All the Layer
3 protocol packets are sent to and processed by the Cisco StackWise Virtual active switch. Both the member switches perform
hardware forwarding for ingress traffic on their interfaces. When software forwarding is required, packets are sent to the
Cisco StackWise Virtual active switch for processing.
The same router MAC address assigned by the Cisco StackWise Virtual active switch is used for all the Layer 3 interfaces
on both the Cisco StackWise Virtual member switches. After a switchover, the original router MAC address is still used. The
router MAC address is chosen based on chassis-mac and is preserved after switchover by default.
The following sections describe the Layer 3 protocols for Cisco StackWise Virtual.
IPv4 Unicast
The CPU on the Cisco StackWise Virtual active switch runs the IPv4 routing protocols and performs any required software forwarding.
All the routing protocol packets received on the Cisco StackWise Virtual standby switch are redirected to the Cisco StackWise
Virtual active switch across the StackWise Virtual link. The Cisco StackWise Virtual active switch generates all the routing
protocol packets to be sent out over ports on either of the Cisco StackWise Virtual member switches.
Hardware forwarding is distributed across both members on Cisco StackWise Virtual. The CPU on the Cisco StackWise Virtual
active switch sends Forwarding Information Base (FIB) updates to the Cisco StackWise Virtual standby switch, which in turn
installs all the routes and adjacencies into hardware.
Packets intended for a local adjacency (reachable by local ports) are forwarded locally on the ingress switch. Packets intended
for a remote adjacency (reachable by remote ports) must traverse the StackWise Virtual link.
The CPU on the Cisco StackWise Virtual active switch performs all software forwarding and feature processing (such as fragmentation
and Time to Live exceed functions). If a switchover occurs, software forwarding is disrupted until the new Cisco StackWise
Virtual active switch obtains the latest Cisco Express Forwarding and other forwarding information.
In virtual switch mode, the requirements to support non-stop forwarding (NSF) match those in the standalone redundant mode
of operation.
From a routing peer perspective, Multi-Chassis EtherChannels (MEC) remain operational during a switchover, that is, only
the links to the failed switch are down, but the routing adjacencies remain valid.
Cisco StackWise Virtual achieves Layer 3 load balancing over all the paths in the Forwarding Information Base entries, be
it local or remote.
IPv6
Cisco StackWise Virtual supports IPv6 unicast and multicast because it is present in the standalone system.
IPv4
Multicast
The IPv4 multicast protocols run on the Cisco StackWise Virtual active switch. Internet Group Management Protocol (IGMP)
and Protocol Independent Multicast (PIM) protocol packets received on the Cisco StackWise Virtual standby switch are transmitted
across a StackWise Virtual link to the Stackwise Virtual active switch. The latter generates IGMP and PIM protocol packets
to be sent over ports on either of the Cisco StackWise Virtual members.
The Cisco StackWise Virtual active switch synchronizes the Multicast Forwarding Information Base (MFIB) state to the Cisco
StackWise Virtual standby switch. On both the member switches, all the multicast routes are loaded in the hardware, with replica
expansion table (RET) entries programmed for only local, outgoing interfaces. Both the member switches are capable of performing
hardware forwarding.
Note
To avoid multicast route changes as a result of a switchover, we recommend that all the links carrying multicast traffic
be configured as MEC rather than Equal Cost Multipath (ECMP).
For packets traversing a StackWise Virtual link, all Layer 3 multicast replications occur on the egress switch. If there
are multiple receivers on the egress switch, only one packet is replicated and forwarded over the StackWise Virtual link,
and then replicated to all the local egress ports.
Software
Features
Software features run only on the Cisco StackWise Virtual active switch. Incoming packets to the Cisco StackWise Virtual
standby switch that require software processing are sent across a StackWise Virtual link to the Cisco StackWise Virtual active
switch.
Dual-Active Detection
If the standby switch detects a complete loss of the StackWise Virtual link, it assumes the active switch has failed and will
take over as the active switch. However, if the original Cisco StackWise Virtual active switch is still operational, both
the switches will now be Cisco StackWise Virtual active switches. This situation is called a dual-active scenario. This scenario
can have adverse effects on network stability because both the switches use the same IP addresses, SSH keys, and STP bridge
IDs. Cisco StackWise Virtual detects a dual-active scenario and takes recovery action. Dual-active-detection link is the dedicated
link used to mitigate this.
If a StackWise Virtual link fails, the Cisco StackWise Virtual standby switch cannot determine the state of the Cisco StackWise
Virtual active switch. To ensure that switchover occurs without delay, the Cisco StackWise Virtual standby switch assumes
that the Cisco StackWise Virtual active switch has failed and initiates switchover to take over the Cisco StackWise Virtual
active role. The original Cisco StackWise Virtual active switch enters recovery mode and brings down all the interfaces except
the StackWise Virtual link and the management interfaces.
Dual-Active-Detection Link with Fast Hello
Note
In Cisco IOS XE Denali 16.3.3, only the fast hello dual-active-detection method is supported.
To use the dual-active fast hello packet detection method, you must provision a direct ethernet connection between the two
Cisco StackWise Virtual switches. You can dedicate up to four links for this purpose.
The two switches periodically exchange special dual-active hello messages containing information about the switch state. If
all Stackwise Virtual Links fail and a dual-active scenario occurs, each switch recognizes that there is a dual-active scenario
from the peer's messages. This initiates recovery actions as described in the Recovery Actions section. If a switch does not receive an expected dual-active fast hello message from the peer before the timer expires,
the switch assumes that the link is no longer capable of dual-active detection.
Note
Do not use the same port for StackWise Virtual link and dual-active detection link.
Recovery Actions
A Cisco Stackwise Virtual active switch that detects a dual-active condition shuts down all of its non-StackWise Virtual Link
interfaces to remove itself from the network. The switch then waits in recovery mode until the StackWise Virtual links have
been recovered. You should physically repair the StackWise Virtual link failure and the recovery switch should be manually
reloaded for it to be the standby switch.
Implementing Cisco StackWise Virtual
The two-node solution of Cisco StackWise Virtual is normally deployed at the aggregation layer. Two switches are connected
over a StackWise Virtual link (SVL).
Cisco StackWise Virtual combines the two switches into a single logical switch with a large number of ports, offering a single
point of management. One of the member switches is the control and management plane master, while the other one is the standby.
The virtualization of multiple physical switches into a single logical switch is only from a control and management perspective.
Because of the control plane being common, it may look like a single logical entity to peer switches. The data plane of the
switches are converged, that is, the forwarding context of a switch might be passed to the other member switch for further
processing when traffic is forwarded across the switches. However, the common control plane ensures that all the switches
have equivalent data plane entry for each forwarding entity.
Figure 2. Two-Node Solution
An election mechanism that determines which switch has Cisco StackWise Virtual active and which one is a control plane standby,
is available. The active switch is responsible for management, bridging and routing protocols, and software data path. These
are centralized on the active switch supervisor of the Cisco StackWise Virtual active switch.
How to Configure Cisco StackWise Virtual
Configuring Cisco StackWise Virtual Settings
To enable StackWise Virtual, perform the following procedure:
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration
mode.
Step 3
stackwise-virtual
Example:
Device(config)# stackwise-virtual
Enables Cisco StackWise Virtual and enters stackwise-virtual submode.
Step 4
domain id
Example:
Device(config-stackwise-virtual)# domain 2
(Optional) Specifies the Cisco StackWise Virtual domain ID.
The domain ID range is from 1 to 255. The default value is one.
What to do next
After the Cisco StackWise Virtual is enabled and the required interfaces are configured on to Cisco StackWise Virtual links,
use the show stackwise-virtual command to verify the configured information. After verification, save the configuration and reboot the switches to form
the stack.
Configuring Cisco StackWise Virtual Link
Note
Cisco StackWise Virtual is supported on port values ranging from 45 to 48 of the 10G interfaces and on all the 40G interfaces.
Note
Cisco StackWise Virtual link is supported on all 10G interfaces, and 40G interfaces. However, a combination of both interfaces
is not supported.
To configure a 10 Gigabit Ethernet port as a StackWise Virtual link port, perform the following procedure:
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
interface TenGigabitEthernet<interface>
Example:
Device(config)#interface TenGigabitEthernet1/0/2
Enters 10G ethernet interface configuration mode.
You can use the interface FortyGigabitEthernet<interface> command for a 40G ethernet interface.
Step 4
stackwise-virtual link
link value
Example:
Device(config-if)#stackwise-virtual link 1
Associates the interface with configured StackWise Virtual link.
Step 5
end
Example:
Device(config-if)#end
Returns to privileged EXEC mode.
Step 6
write memory
Example:
Device#write memory
Saves the running-configuration which resides in the system RAM to the startup-configuration in the system NVRAM. If you do
not save the changes, the changes will no longer be part of the startup configuration when the switch reloads.
Step 7
reload
Example:
Device#reload
Restarts the switch.
Configuring a StackWise Virtual Dual-Active-Detection link
To configure a 10 Gigabit Ethernet port as StackWise dual-active-detection link, perform the following procedure. This procedure
is optional.
Procedure
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configureterminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
interface TenGigabitEthernet<interface>
Example:
Device(config)#interface TenGigabitEthernet1/0/41
Enters a 10G interface configuration mode.
Note
1G interfaces can also be configured as Dual-active detection link.
You must use different ports for StackWise Virtual link and dual-active detection link.
Associates the interface with StackWise Virtual dual-active-detection.
Note
This command will not be visible on the device after the configuration, but will continue to function.
Step 5
end
Example:
Device(config-if)#end
Returns to privileged EXEC mode.
Step 6
write memory
Example:
Device#write memory
Saves the running-configuration which resides in the system RAM to the startup-configuration in the system NVRAM. If you do
not save the changes, the changes will no longer be part of the startup configuration when the switch reloads.
Step 7
reload
Example:
Device#reload
Restarts the switch.
Verifying Cisco StackWise Virtual Configuration
To verify your Stackwise Virtual configuration, use the following show commands:
show stackwise-virtual switch number <1-2>
Displays information of a particular switch in the stack.
show stackwise-virtual link
Displays StackWise Virtual link information.
show stackwise-virtual bandwidth
Displays the bandwidth available for the Cisco StackWise Virtual.