Your software release might not support all the features documented in this module. For the latest caveats and feature information, see the Bug Search Tool at https://tools.cisco.com/bugsearch/ and the release notes for your software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the New and Changed chapter or the Feature History table below.

PortChannels refer to the aggregation of multiple physical interfaces into one logical interface to provide higher aggregated bandwidth, load balancing, and link redundancy (see Figure 1). PortChannels can connect to interfaces across switching modules, so a failure of a switching module cannot bring down the PortChannel link.

PortChannels on Cisco MDS 9000 Series Multilayer Switches allow flexibility in configuration. This illustrates three possible PortChannel configurations:

• PortChannel A aggregates two links on two interfaces on the same switching module at each end of a connection.

• PortChannel B also aggregates two links, but each link is connected to a different switching module. If the switching module goes down, traffic is not affected.

• PortChannel C aggregates three links. Two links are on the same switching module at each end, while one is connected to a different switching module on switch 2.

An E PortChannel refers to the aggregation of multiple E ports into one logical interface to provide higher aggregated bandwidth, load balancing, and link redundancy. PortChannels can connect to interfaces across switching modules, so a failure of a switching module cannot bring down the PortChannel link.

A PortChannel has the following features and restrictions:

• Provides a point-to-point connection over ISL (E ports) or EISL (TE ports). Multiple links can be combined into a PortChannel.

• Increases the aggregate bandwidth on an ISL by distributing traffic among all functional links in the channel.

• Load balances across multiple links and maintains optimum bandwidth utilization. Load balancing is based on the source ID, destination ID, and exchange ID (OX ID).

• Provides high availability on an ISL. If one link fails, traffic previously carried on this link is switched to the remaining links. If a link goes down in a PortChannel, the upper protocol is not aware of it. To the upper protocol, the link is still there, although the bandwidth is diminished. The routing tables are not affected by link failure. PortChannels may contain up to 16 physical links and may span multiple modules for added high availability.

Note	See the Cisco MDS 9000 Series NX-OS Fabric Configuration Guide for information about failover scenarios for PortChannels and FSPF links.

An F PortChannel is also a logical interface that combines a set of F ports connected to the same Fibre Channel node and operates as one link between the F ports and the NP ports. The F PortChannels support bandwidth utilization and availability like the E PortChannels. F PortChannels are mainly used to connect MDS core and NPV switches to provide optimal bandwidth utilization and transparent failover between the uplinks of a VSAN.

An F PortChannel trunk combines the functionality and advantages of a TF port and an F PortChannel. This logical link uses the Cisco PTP and PCP protocols over Cisco EPP (ELS).

Note	If a Cisco MDS 9124 or 9134 switch is used as a core switch, only a nontrunking F PortChannel is supported. Trunking is not supported on this platform when NPIV enabled.

Trunking is a commonly used storage industry term. However, the Cisco NX-OS software and switches in the Cisco MDS 9000 Series Multilayer Switches implement trunking and PortChanneling as follows:

• PortChanneling enables several physical links to be combined into one aggregated logical link.

• Trunking enables a link transmitting frames in the EISL format to carry (trunk) multiple VSAN traffic. For example, when trunking is operational on an E port, that E port becomes a TE port. A TE port is specific to switches in the Cisco MDS 9000 Series Multilayer Switches. An industry standard E port can link to other vendor switches and is referred to as a nontrunking interface (see Figure 1 and Figure 2). See Configuring Trunking for information on trunked interfaces.

PortChanneling and trunking are used separately across an ISL.

• PortChanneling—Interfaces can be channeled between the following sets of ports:

  • E ports and TE ports

  • F ports and NP ports

  • TF ports and TNP ports

• Trunking—Trunking permits carrying traffic on multiple VSANs between switches.

See the Cisco MDS 9000 Series NX-OS Fabric Configuration Guide.

• Both PortChanneling and trunking can be used between TE ports over EISLs.

Two methods support the load-balancing functionality:

• Flow based—All frames between source and destination follow the same links for a given flow. That is, whichever link is selected for the first exchange of the flow is used for all subsequent exchanges.

• Exchange based—The first frame in an exchange picks a link and subsequent frames in the exchange follow the same link. However, subsequent exchanges can use a different link. This provides more granular load balancing while preserving the order of frames for each exchange.

Figure 1 illustrates how source ID 1 (SID1) and destination ID1 (DID1) based load balancing works. When the first frame in a flow is received on an interface for forwarding, link 1 is selected. Each subsequent frame in that flow is sent over the same link. No frame in SID1 and DID1 utilizes link 2.

Figure 2 illustrates how exchange-based load balancing works. When the first frame in an exchange is received for forwarding on an interface, link 1 is chosen by a hash algorithm. All remaining frames in that particular exchange are sent on the same link. For exchange 1, no frame uses link 2. For the next exchange, link 2 is chosen by the hash algorithm. Now all frames in exchange 2 use link 2.

For more information on configuring load balancing and in-order delivery features, see the Cisco MDS 9000 Series NX-OS Fabric Configuration Guide.

You can configure each PortChannel with a channel group mode parameter to determine the PortChannel protocol behavior for all member ports in this channel group. The possible values for a channel group mode are as follows:

• ON (default)—The member ports only operate as part of a PortChannel or remain inactive. In this mode, the PortChannel protocol is not initiated. However, if a PortChannel protocol frame is received from a peer port, the software indicates its nonnegotiable status. This mode is backward compatible with the existing implementation of PortChannels in releases prior to Release 2.0(1b), where the channel group mode is implicitly assumed to be ON. In Cisco MDS SAN-OS Releases 1.3 and earlier, the only available PortChannel mode was the ON mode. PortChannels configured in the ON mode require you to explicitly enable and disable the PortChannel member ports at either end if you add or remove ports from the PortChannel configuration. You must physically verify that the local and remote ports are connected to each other.
• ACTIVE—The member ports initiate PortChannel protocol negotiation with the peer port(s) regardless of the channel group mode of the peer port. If the peer port, while configured in a channel group, does not support the PortChannel protocol, or responds with a nonnegotiable status, it will default to the ON mode behavior. The ACTIVE PortChannel mode allows automatic recovery without explicitly enabling and disabling the PortChannel member ports at either end.

Table 1 compares ON and ACTIVE modes.

When you delete the PortChannel, the corresponding channel membership is also deleted. All interfaces in the deleted PortChannel convert to individual physical links. After the PortChannel is removed, regardless of the mode used (ACTIVE and ON), the ports at either end are gracefully brought down, indicating that no frames are lost when the interface is going down (see the Graceful Shutdown).

If you delete the PortChannel for one port, then the individual ports within the deleted PortChannel retain the compatibility parameter settings (speed, mode, port VSAN, allowed VSAN, and port security). You can explicitly change those settings as required.

• If you use the default ON mode to avoid inconsistent states across switches and to maintain consistency across switches, then the ports shut down. You must explicitly enable those ports again.
• If you use the ACTIVE mode, then the PortChannel ports automatically recover from the deletion.

You can add or remove a physical interface (or a range of interfaces) to an existing PortChannel. The compatible parameters on the configuration are mapped to the PortChannel. Adding an interface to a PortChannel increases the channel size and bandwidth of the PortChannel. Removing an interface from a PortChannel decreases the channel size and bandwidth of the PortChannel.

Note	For information about PortChannel support on Generation 2 switching modules, see the PortChannel Limitations.

In earlier Cisco SAN-OS releases, PortChannels required additional administrative tasks to support synchronization. The Cisco NX-OS software provides robust error detection and synchronization capabilities. You can manually configure channel groups or they can be automatically created. In both cases, the channel groups have the same capability and configurational parameters. Any change in configuration applied to the associated PortChannel interface is propagated to all members of the channel group.

A protocol to exchange PortChannel configurations is available in all Cisco MDS switches. This addition simplifies PortChannel management with incompatible ISLs. An additional autocreation mode enables ISLs with compatible parameters to automatically form channel groups without manual intervention.

The PortChannel protocol is enabled by default.

The PortChannel protocol expands the PortChannel functional model in Cisco MDS switches. It uses the exchange peer parameters (EPP) services to communicate across peer ports in an ISL. Each switch uses the information received from the peer ports along with its local configuration and operational values to decide if it should be part of a PortChannel. The protocol ensures that a set of ports are eligible to be part of the same PortChannel. They are only eligible to be part of the same PortChannel if all the ports have a compatible partner.

The PortChannel protocol uses two subprotocols:

• Bringup protocol—Automatically detects misconfigurations so you can correct them. This protocol synchronizes the PortChannel at both ends so that all frames for a given flow (as identified by the source FC ID, destination FC ID and OX_ID) are carried over the same physical link in both directions. This helps make applications such as write acceleration, work for PortChannels over FCIP links.

• Autocreation protocol—Automatically aggregates compatible ports into a PortChannel.

Before configuring a PortChannel, consider the following guidelines:

• Configure the PortChannel across switching modules to implement redundancy on switching module reboots or upgrades.
• Ensure that one PortChannel is not connected to different sets of switches. PortChannels require point-to-point connections between the same set of switches.

Note

On switches with Generation 1 switching modules, or a combination of Generation 1 and Generation 2 switching modules, you can configure a maximum of 128 PortChannels. On switches with only Generation 2 switching modules, or Generation 2 and Generation 3 switching modules, you can configure a maximum of 256 PortChannels.

If you misconfigure PortChannels, you may receive a misconfiguration message. If you receive this message, the PortChannel’s physical links are disabled because an error has been detected.

A PortChannel error is detected if the following requirements are not met:

• Each switch on either side of a PortChannel must be connected to the same number of interfaces.
• Each interface must be connected to a corresponding interface on the other side (see Figure 2 for an example of an invalid configuration).
• Links in a PortChannel cannot be changed after the PortChannel is configured. If you change the links after the PortChannel is configured, be sure to reconnect the links to interfaces within the PortChannel and reenable the links.

If all three conditions are not met, the faulty link is disabled.

Enter the show interface command for that interface to verify that the PortChannel is functioning as required.

Table 1 lists the default settings for PortChannels.

Cisco MDS 9000 Series Multilayer switches support the following number of PortChannels per switch:

• Switches with only Generation 1 switching modules do not support F and TF PortChannels.

• Switches with Generation 1 switching modules, or a combination of Generation 1 and Generation 2 switching modules, support a maximum of 128 PortChannels. Only Generation 2 ports can be included in the PortChannels.

• Switches with only Generation 2 switching modules or Generation 2 and Generation 3 modules support a maximum of 256 PortChannels with 16 interfaces per PortChannel.

• A PortChannel number refers to the unique identifier for each channel group. This number ranges from of 1 to 256.

This section includes the restrictions on creation and addition of PortChannel members to a PortChannel on Generation 1 hardware:

• The 32-port 2-Gbps or 1-Gbps switching module.
• The MDS 9140 and 9120 switches.

When configuring the host-optimized ports on Generation 1 hardware, the following PortChannel guidelines apply:

• If you execute the write erase command on a 32-port switching module, and then copy a saved configuration to the switch from a text file that contains the no system default switchport shutdown command, you need to copy the text file to the switch again for the E ports to come up without manual configuration.
• Any (or all) full line rate port(s) in the Cisco MDS 9100 Series can be included in a PortChannel.
• The host-optimized ports in the Cisco MDS 9100 Series are subject to the same PortChannel rules as 32-port switching modules; only the first port of each group of 4 ports is included in a PortChannel.
  • You can configure only the first port in each 4-port group as an E port (for example, the first port in ports 1–4, the fifth port in ports 5–8, and so on). If the first port in the group is configured as a PortChannel, the other three ports in each group (ports 2–4, 6–8, and so on) are not usable and remain in the shutdown state.
  • If any of the other three ports are configured in a no shutdown state, you cannot configure the first port to be a PortChannel. The other three ports continue to remain in a no shutdown state.

The following guidelines and restrictions are applicable for F and TF PortChannels:

• The ports must be in F mode.
• Automatic creation is not supported.
• The PortChannel interface must be in ACTIVE mode when multiple FCIP interfaces are grouped with WA.
• ON mode is not supported. Only ACTIVE-ACTIVE mode is supported. By default, the mode is ACTIVE on the NPV switches.
• Devices logged in through F PortChannel on an MDS switch are not supported in IVR non-NAT configuration. The devices are supported only in IVR NAT configuration.
• Port security rules are enforced only on physical pWWNs at the single link level.
• FC-SP authenticates only the first physical FLOGI of every PortChannel member.
• Since the FLOGI payload carries only the VF bits to trigger the use of a protocol after the FLOGI exchange, those bits will be overridden. In the case of the NPV switches, the core has a Cisco WWN and will try to initiate the PCP protocol.
• The name server registration of the N ports logging in through an F PortChannel will use the fWWN of the PortChannel interface.
• DPVM configuration is not supported.
• The PortChannel port VSAN cannot be configured using DPVM.
• The Dynamic Port VSAN Management (DPVM) database will be queried only for the first physical FLOGI of each member, so that the port VSAN can be configured automatically.
• DPVM does not bind FC_IDs to VSANs, but pWWNs to VSANs. It will be queried only for the physical FLOGI.

PortChannels are created with default values. You can change the default configuration just like any other physical interface.

Figure 1 provides examples of valid PortChannel configurations.

Figure 2 provides examples of invalid configurations. Assuming that the links are brought up in the 1, 2, 3, 4 sequence, links 3 and 4 will be operationally down as the fabric is misconfigured.

You can convert autocreated channel group to a user-configured channel group using the port-channel channel-group-number persistent EXEC command. If the PortChannel does not exist, this command is not executed.

To display PortChannel configuration information, perform one of the following tasks:

For detailed information about the fields in the output from these commands, refer to the Cisco MDS 9000 Series NX-OS Command Reference.

You can view specific information about existing PortChannels at any time from EXEC mode. The following show commands provide further details on existing PortChannels. You can force all screen output to go to a printer or save it to a file. See Examples Displays the PortChannel Summary to Displays the PortChannel Summary.

switch# show port-channel summary
 ------------------------------------------------------------------------------
Interface                 Total Ports        Oper Ports        First Oper Port
------------------------------------------------------------------------------
port-channel 77                2                 0                  --
port-channel 78                2                 0                  --
port-channel 79                2                 2                  fcip200

switch# show port-channel database
 
port-channel 77
    Administrative channel mode is on
    Operational channel mode is on
    Last membership update succeeded
    2 ports in total, 0 ports up
    Ports:   fcip1    [down]
             fcip2    [down]
port-channel 78
    Administrative channel mode is on
    Operational channel mode is on
    Last membership update succeeded
    2 ports in total, 0 ports up
    Ports:   fc2/1    [down]
             fc2/5    [down]
port-channel 79
    Administrative channel mode is on
    Operational channel mode is on
    Last membership update succeeded
    First operational port is fcip200
    2 ports in total, 2 ports up
    Ports:   fcip101  [up]
             fcip200  [up] *

switch# show port-channel database
 
port-channel 77
    Administrative channel mode is active
    Operational channel mode is active
    Last membership update succeeded
    2 ports in total, 0 ports up
    Ports:   fcip1    [down]
             fcip2    [down]
port-channel 78
    Administrative channel mode is active
    Operational channel mode is active
    Last membership update succeeded
    2 ports in total, 0 ports up
    Ports:   fc2/1    [down]
             fc2/5    [down]
port-channel 79
    Administrative channel mode is active
    Operational channel mode is active
    Last membership update succeeded
    First operational port is fcip200
    2 ports in total, 2 ports up
    Ports:   fcip101  [up]
             fcip200  [up] *

switch# show port-channel consistency
Database is consistent

switch# show port-channel consistency detail
Authoritative port-channel database:
================================================
totally 3 port-channels
port-channel 77:
    2 ports, first operational port is none
    fcip1    [down]
    fcip2    [down]
port-channel 78:
    2 ports, first operational port is none
    fc2/1    [down]
    fc2/5    [down]
port-channel 79:
    2 ports, first operational port is fcip200
    fcip101  [up]
    fcip200  [up]
================================================
database 1: from module 5
================================================
totally 3 port-channels
port-channel 77:
    2 ports, first operational port is none
    fcip1    [down]
    fcip2    [down]
port-channel 78:
    2 ports, first operational port is none
    fc2/1    [down]
    fc2/5    [down]
port-channel 79:
    2 ports, first operational port is fcip200
    fcip101  [up]
    fcip200  [up]
================================================
database 2: from module 4
================================================
totally 3 port-channels
port-channel 77:
    2 ports, first operational port is none
    fcip1    [down]
    fcip2    [down]
port-channel 78:
    2 ports, first operational port is none
    fc2/1    [down]
    fc2/5    [down]
port-channel 79:
    2 ports, first operational port is fcip200
    fcip101  [up]
    fcip200  [up]
...

switch# show port-channel usage 
Totally 3 port-channel numbers used
===================================
Used  :   77 - 79
Unused:   1 - 76 , 80 - 256

switch# show port-channel compatibility-parameters
physical port layer                 fibre channel or ethernet
    port mode                           E/AUTO only
    trunk mode
    speed
    port VSAN
    port allowed VSAN list

switch# show interface fc1/1
fc1/1 is trunking
    Hardware is Fibre Channel, FCOT is short wave laser
    Port WWN is 20:0a:00:0b:5f:3b:fe:80
    ...
    Receive data field Size is 2112
    Beacon is turned off
    Port-channel auto creation is enabled
	Belongs to port-channel 123
...

switch# show port-channel database interface port-channel 128
port-channel 128
    Administrative channel mode is active
    Operational channel mode is active
    Last membership update succeeded
    Channel is auto created
    First operational port is fc1/1
    1 ports in total, 1 ports up
    Ports:   fc1/1   [up] *

switch# show port-channel summary
------------------------------------------------------------------------------
Interface                 Total Ports        Oper Ports        First Oper Port
------------------------------------------------------------------------------
port-channel 1                 1                 0                  --
port-channel 2                 1                 1                  fc8/13
port-channel 3                 0                 0                  --
port-channel 4                 0                 0                  --
port-channel 5                 1                 1                  fc8/3
port-channel 6                 0                 0                  --