Cisco MDS 9000 Family Fabric Manager Configuration Guide
Configuring Port Channels
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Configuring PortChannels

Table Of Contents

Configuring PortChannels

About PortChannels

About E PortChannels

About F and TF PortChannels

About PortChanneling and Trunking

About Load Balancing

About PortChannel Modes

Configuration Guidelines and Restrictions

Generation 1 PortChannel Restrictions

F and TF PortChannel Restrictions

PortChannel Configuration

About PortChannel Configuration

Configuring PortChannels Using the Wizard

Configuring the PortChannel Mode

About PortChannel Deletion

Deleting PortChannels

Interfaces in a PortChannel

About Interface Addition to a PortChannel

Compatibility Check

Suspended and Isolated States

Adding an Interface to a PortChannel

Forcing an Interface Addition

About Interface Deletion from a PortChannel

Deleting an Interface from a PortChannel

PortChannel Protocols

About Channel Group Creation

About Autocreation

Enabling and Configuring Autocreation

About Manually Configured Channel Groups

Converting to Manually Configured Channel Groups

Verifying the PortChannel Configuration

Default Settings


Configuring PortChannels


This chapter discusses the PortChannel feature provided in the switch and includes the following sections:

About PortChannels

PortChannel Configuration

Interfaces in a PortChannel

PortChannel Protocols

Verifying the PortChannel Configuration

Default Settings

About PortChannels

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 23-1). PortChannels can connect to interfaces across switching modules, so a failure of a switching module cannot bring down the PortChannel link.

Figure 23-1 PortChannel Flexibility

PortChannels on Cisco MDS 9000 Family switches allow flexibility in configuration. Figure 23-1 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.

This section contains the following topics:

About E PortChannels

About F and TF PortChannels

About PortChanneling and Trunking

About Load Balancing

About PortChannel Modes

Configuration Guidelines and Restrictions

About E PortChannels

An E PortChannel refers to the aggregation of multiple physical Ethernet interfaces 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 "Fail-Over Scenarios for PortChannels and FSPF Links" section on page 31-3 for failover scenarios.


About F and TF PortChannels

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 port channels support bandwidth utilization and availability like the E port channels. 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.


About PortChanneling and Trunking

Trunking is a commonly used storage industry term. However, the Cisco NX-OS software and switches in the Cisco MDS 9000 Family 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 Family. An industry standard E port can link to other vendor switches and is referred to as a nontrunking interface (see Figure 23-2 and Figure 23-3).

See Chapter 24, "Configuring Trunking," for information on trunked interfaces.

Figure 23-2 Trunking Only

PortChanneling and trunking are used separately across an ISL:

Figure 23-3 PortChanneling and Trunking

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 Chapter 26, "Configuring and Managing VSANs."

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

About Load Balancing

Two mechanisms 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 23-4 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 23-4 SID1 and DID1 Based Load Balancing

Figure 23-5 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.

Figure 23-5 SID1, DID1, and Exchange Based Load Balancing

For more information on configuring load balancing and in-order delivery features, see the "About VSANs" section on page 26-1.

About PortChannel Modes

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 23-1 compares ON and ACTIVE modes.

Table 23-1 Channel Group Configuration Differences 

ON Mode
ACTIVE Mode

No protocol is exchanged.

A PortChannel protocol negotiation is performed with the peer ports.

Moves interfaces to the suspended state if its operational values are incompatible with the PortChannel.

Moves interfaces to the isolated state if its operational values are incompatible with the PortChannel.

When you add or modify a PortChannel member port configuration, you must explicitly disable (shut) and enable (no shut) the PortChannel member ports at either end.

When you add or modify a PortChannel interface, the PortChannel automatically recovers.

Port initialization is not synchronized.

There is synchronized startup of all ports in a channel across peer switches.

All misconfigurations are not detected as no protocol is exchanged.

Consistently detect misconfigurations using a PortChannel protocol.

Transitions misconfigured ports to the suspended state. You must explicitly disable (shut) and enable (no shut) the member ports at either end.

Transitions misconfigured ports to the isolated state to correct the misconfiguration. Once you correct the misconfiguration, the protocol ensures automatic recovery.

This is the default mode.

You must explicitly configure this mode.


Configuration Guidelines and Restrictions

Cisco MDS 9000 Family 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.

Generation 1 PortChannel Restrictions

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

32-port 2-Gbps or 1-Gbps switching module

MDS 9124 and 9134 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.

F and TF PortChannel Restrictions

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.

Switches must be running NX-OS Release 4.1(1a) or later.

PortChannel Configuration

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

Figure 23-6 provides examples of valid PortChannel configurations.

Figure 23-6 Valid PortChannel Configurations

Figure 23-7 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.

Figure 23-7 Misconfigured Configurations

This section shows how to configure and modify PortChannels and contains the following topics:

About PortChannel Configuration

Configuring PortChannels Using the Wizard

About PortChannel Modes

About PortChannel Deletion

Deleting PortChannels

About PortChannel Configuration

Before configuring a PortChannel, consider the following guidelines:

Configure the PortChannel across switching modules to prevent 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 23-7 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.

Configuring PortChannels Using the Wizard

To create a PortChannel using the PortChannel Wizard in Fabric Manager, follow these steps:


Step 1 Click the PortChannel Wizard icon in the toolbar (see Figure 23-8).

Figure 23-8 PortChannel Wizard Icon

You see the first PortChannel Wizard screen.

Step 2 Select a switch pair. Figure 23-9 shows a list of the switch pairs.

Figure 23-9 Select Switch Pairs

Step 3 Click Next.

Step 4 Select the ISLs. Figure 23-10 shows a list of the ISLs.

Figure 23-10 Select ISLs

Step 5 (Optional) Check the Dynamically form Port Channel Group from selected ISLs check box if you want to dynamically create the PortChannel and make the ISL properties identical for the Admin, Trunk, Speed, and VSAN attributes.

Step 6 Click Next.

Step 7 If you chose to dynamically form a PortChannel from selected ISLs, you see the final PortChannel Wizard screen (see Figure 23-11). Set the VSAN List, Trunk Mode, and Speed and proceed to Step 11.

Figure 23-11 Dynamically Form a PortChannel

Step 8 If you did not choose to dynamically form a PortChannel, you see the third PortChannel Wizard dialog box(see Figure 23-12).


Note Dynamic VSAN creation is not supported on NPV switches.


Figure 23-12 Create a PortChannel

Step 9 Change the channel ID or description for each switch, if necessary.

Step 10 Review the attributes at the bottom of the screen, and set them if applicable.

The following attributes are shown in Figure 23-12:

VSAN List—This gives a list of VSANs to which the ISLs belong.

Trunk Mode—You can enable trunking on the links in the PortChannel. Select trunking if your link is between TE ports. Select nontrunking if your link is between E ports. Select auto if you are not sure.

Force Admin, Trunk, Speed, and VSAN attributes to be identical—This check box ensures that the same parameter settings are used in all physical ports in the channel. If these settings are not identical, the ports cannot become part of the PortChannel.

Speed—The port speed values are auto, 1Gb, 2Gb, 4Gb, 8Gb, autoMax2G, and autoMax4G.

Step 11 Click OK.

The PortChannel is created. Note that it may take a few minutes before the new PortChannel is visible in the Fabric pane.


Configuring the PortChannel Mode

By default, the CLI and the Device Manager create the PortChannel in ON mode in the NPIV core switches and ACTIVE mode on the NPV switches. The Fabric Manager creates all PortChannels in ACTIVE mode. We recommend that you create PortChannels in ACTIVE mode. An F PortChannel is supported only on ACTIVE mode.

To configure ACTIVE mode using Fabric Manager, follow these steps:


Step 1 Expand ISLs and then select Port Channels in the Physical Attributes pane.

You see the PortChannels configured in the Information pane.

Step 2 Click the Protocols tab, and then from the Mode drop-down menu, select the appropriate mode for the Port Channel.

Step 3 Click the Apply Changes icon to save any modifications.


About PortChannel Deletion

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" section on page 20-11).

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.

Deleting PortChannels

To delete a PortChannel using the PortChannel Wizard in Fabric Manager, follow these steps:


Step 1 Click the PortChannel Wizard icon in the toolbar (see Figure 23-13).

Figure 23-13 PortChannel Wizard Icon

You see the first PortChannel Wizard screen.

Step 2 Select the existing PortChannel that you want to delete and click Next. You see a list of the ISLs currently associated with this PortChannel.

Step 3 Click Next. You see an editable list of associated ISLs and available ISLs for this PortChannel.

Step 4 Click each associated ISL and click the left arrow to remove all ISLs from the PortChannel.

Step 5 Check the Delete Port Channel If Empty check box to delete this PortChannel.

Step 6 Click Finish to save any modifications or click Cancel to discard any changes.


Interfaces in a PortChannel

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.

This section describes interface configuration for a PortChannel and includes the following topics:

About Interface Addition to a PortChannel

Adding an Interface to a PortChannel

Forcing an Interface Addition

About PortChannel Deletion

Deleting an Interface from a PortChannel

About Interface Addition to a PortChannel

You can add 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.

A port can be configured as a member of a static PortChannel only if the following configurations are the same in the port and the PortChannel:

Speed

Mode

Rate mode

Port VSAN

Trunking mode

Allowed VSAN list or VF-ID list

After the members are added, regardless of the mode (ACTIVE and ON) used, the ports at either end are gracefully brought down, indicating that no frames are lost when the interface is going down (see the "Generation 1 PortChannel Restrictions" section and "Graceful Shutdown" section on page 20-11).

Compatibility Check

A compatibility check ensures that the same parameter settings are used in all physical ports in the channel. Otherwise, they cannot become part of a PortChannel. The compatibility check is performed before a port is added to the PortChannel.

The check ensures that the following parameters and settings match at both ends of a PortChannel:

Capability parameters (type of interface, Gigabit Ethernet at both ends, or Fibre Channel at both ends).

Administrative compatibility parameters (speed, mode, rate mode, port VSAN, allowed VSAN list, and port security).


Note Ports in shared rate mode can also form a PortChannel or a trunking PortChannel.


Operational parameters (remote switch WWN and trunking mode).

A port addition procedure fails if the capability and administrative parameters in the remote switch are incompatible with the capability and administrative parameters in the local switch. If the compatibility check is successful, the interfaces are operational and the corresponding compatibility parameter settings apply to these interfaces.

Suspended and Isolated States

If the operational parameters are incompatible, the compatibility check fails and the interface is placed in a suspended or isolated state based on the configured mode:

An interface enters the suspended state if the interface is configured in the ON mode.

An interface enters the isolated state if the interface is configured in the ACTIVE mode.

See the "Reason Codes" section on page 20-8.

Adding an Interface to a PortChannel


Note By default, the CLI adds a interface normally to a PortChannel, while the Fabric Manager adds the interface by force, unless specified explicitly.


To add an interface or range of interfaces to a PortChannel using Fabric Manager, follow these steps:


Step 1 Expand ISLs and then select Port Channels in the Physical Attributes pane.

You see the PortChannels configured in the Information pane (see Figure 23-14).

Figure 23-14 Port Channels

Step 2 Click the Channels tab and find the switch and PortChannel that you want to edit.

Step 3 Set Members Admin to the interface or list of interfaces that you want to add to the PortChannel.

Step 4 Click the Apply Changes icon to save any modifications or click Undo Changes to discard any changes.


Forcing an Interface Addition

You can force the port configuration to be overwritten by the PortChannel. In this case, the interface is added to a PortChannel.

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 addition.


Note When PortChannels are created from within an interface, the force option cannot be used.


After the members are forcefully added, regardless of the mode (ACTIVE and ON) used, the ports at either end are gracefully brought down, indicating that no frames are lost when the interface is going down.

To force the addition of a port to a PortChannel using Fabric Manager, follow these steps:


Step 1 Expand ISLs and then select Port Channels in the Physical Attributes pane. You see the PortChannels configured in the Information pane.

Step 2 Click the Channels tab and find the switch and PortChannel that you want to edit.

Step 3 Set Members Admin to the interface or list of interfaces that you want to add to the PortChannel.

Step 4 Check the Force check box to force this interface addition.

Step 5 Click the Apply Changes icoon to save any modifications.


About Interface Deletion from a PortChannel

When a physical interface is deleted from the PortChannel, the channel membership is automatically updated. If the deleted interface is the last operational interface, then the PortChannel status is changed to a down state. Deleting an interface from a PortChannel decreases the channel size and bandwidth of the PortChannel.

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.

After the members are deleted, regardless of the mode (ACTIVE and ON) used, the ports at either end are gracefully brought down, indicating that no frames are lost when the interface is going down (see the "Generation 1 PortChannel Restrictions" section and "Graceful Shutdown" section on page 20-11).

Deleting an Interface from a PortChannel

To delete a physical interface (or a range of physical interfaces) from a PortChannel using Fabric Manager, follow these steps:


Step 1 Expand ISLs and then select Port Channels in the Physical Attributes pane.

You see the PortChannels configured in the Information pane.

Step 2 Click the Channels tab and find the switch and PortChannel that you want to edit.

Step 3 Remove the interface or list of interfaces you want deleted in the Members the Admin column.

Step 4 Click the Apply Changes icon to save any modifications.


PortChannel Protocols

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 port channel 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.

This section describes how to configure the PortChannel protocol and includes the following sections:

About Channel Group Creation

About Autocreation

Enabling and Configuring Autocreation

About Manually Configured Channel Groups

Converting to Manually Configured Channel Groups

About Channel Group Creation


Note Channel groups are not supported on internal ports in the Cisco Fabric Switch for HP c-Class BladeSystem and the Cisco Fabric Switch for IBM BladeSystem.


Assuming link A1-B1 comes up first in Figure 23-15, that link is operational as an individual link.When the next link, say A2-B2 comes up, the PortChannel protocol identifies if this link is compatible with link A1-B1 and automatically creates channel groups 10 and 20 in the respective switches. If link A3-B3 can join the channel groups (the PortChannels), the respective ports have compatible configurations. If link A4-B4 operates as an individual link, it is because of the incompatible configuration of the two end ports with the other member ports in this channel group.

Figure 23-15 Autocreating Channel Groups

The channel group numbers are selected dynamically, and as such, the administrative configuration of the ports forming the channel group at either end are applicable to the newly created channel group. The channel group number being chosen dynamically may be different across reboots for the same set of PortChannels based on the order of ports that are initialized in the switch.

Table 23-2 identifies the differences between user-configured and auto-configured channel groups.

Table 23-2 Channel Group Configuration Differences 

User-Configured Channel Group
Autocreated Channel Group

Manually configured by the user.

Created automatically when compatible links come up between two compatible switches, if channel group autocreation is enabled in all ports at both ends.

Member ports cannot participate in autocreation of channel groups. The autocreation feature cannot be configured.

None of these ports are members of a user-configured channel group.

You can form the PortChannel with a subset of the ports in the channel group. Incompatible ports remain in a suspended or isolated state depending on the ON or ACTIVE mode configuration.

All ports included in the channel group participate in the PortChannel—no member port becomes isolated or suspended; instead, the member port is removed from the channel group when the link is found to be incompatible.

Any administrative configuration made to the PortChannel is applied to all ports in the channel group, and you can save the configuration for the PortChannel interface.

Any administrative configuration made to the PortChannel is applied to all ports in the channel group, but the configurations are saved for the member ports; no configuration is saved for the PortChannel interface. You can explicitly convert this channel group, if required.

You can remove any channel group and add members to a channel group.

You cannot remove a channel group, or add/remove any of its members. The channel group is removed when no member ports exist.



Note Autocreation is not supported as of MDS NX-OS Release 4.1(1b) and later.


About Autocreation

The autocreation protocol has the following functionality:

A port is not allowed to be configured as part of a PortChannel when the autocreation feature is enabled. These two configurations are mutually exclusive.

Autocreation must be enabled in both the local and peer ports to negotiate a PortChannel.

Aggregation occurs in one of two ways:

A port is aggregated into a compatible autocreated PortChannel.

A port is aggregated with another compatible port to form a new PortChannel.

Newly created PortChannels are allocated from the maximum possible PortChannel (128 for Generation 1 or a combination of Generation 1 and Generation 2 switches, or 256 for Generation 2 switches) in a decreasing order based on availability. If all 128 (or 256) numbers are used up, aggregation is not allowed.

You cannot change the membership or delete an autocreated PortChannel.

When you disable autocreation, all member ports are removed from the autocreated PortChannel.

Once the last member is removed from an autocreated PortChannel, the channel is automatically deleted and the number is released for reuse.

An autocreated PortChannel is not persistent through a reboot. An autocreated PortChannel can be manually configured to appear the same as a persistent PortChannel. Once the PortChannel is made persistent, the autocreation feature is disabled in all member ports.

You can enable or disable the autocreation feature on a per-port basis or for all ports in the switch. When this configuration is enabled, the channel group mode is assumed to be active. The default for this task is disabled.

If autocreation of channel groups is enabled for an interface, you must first disable autocreation before downgrading to earlier software versions or before configuring the interface in a manually configured channel group.


Tip When enabling autocreation in any switch in the Cisco MDS 9000 Family, we recommend that you retain at least one interconnected port between the switches without any autocreation configuration. If all ports between two switches are configured with the autocreation feature at the same time, you may face a possible traffic disruption between these two switches as the ports are automatically disabled and reenabled when ports are added to an autocreated PortChannel.


Enabling and Configuring Autocreation

To configure PortChannel autocreation, check the Dynamically form Port Channel Group from selected ISLs option in the PortChannel Wizard. For more information, see the "Configuring PortChannels Using the Wizard" section.

About Manually Configured Channel Groups

A user-configured channel group cannot be converted to an autocreated channel group. However, you can convert an autocreated channel group to a manual channel group. Once performed, this task is irreversible. The channel group number does not change, but the member ports operate according to the properties of the manually configured channel group, and the autocreation of channel group is implicitly disabled for all member ports.


Tip If you enable persistence, be sure to enable it at both ends of the PortChannel.


Converting to Manually Configured Channel Groups

To convert an autocreated channel group to a user-configured channel group using Fabric Manager, follow these steps:


Step 1 Expand ISLs and then select Port Channels in the Physical Attributes pane. Click the Protocol tab.

You see the switch protocols as shown in Figure 23-16.

Figure 23-16 Switch Protocols

Step 2 Check the Persist check box for each channel that you want to convert to a manually configured channel group.

Step 3 Click the Apply Changes icon to save any modifications.





Verifying the PortChannel Configuration


You can use the Information pane in Fabric Manager to verify your PortChannel Configuration (see Figure 23-17).

Figure 23-17 PortChannel Summary in Fabric Manager

Default Settings

Table 23-3 lists the default settings for PortChannels.

Table 23-3 Default PortChannel Parameters 

Parameters
Default

PortChannels

FSPF is enabled by default.

Create PortChannel

Administratively up.

Default PortChannel mode

ON mode on non-NPV and NPIV core switches.

ACTIVE mode on NPV switches.

Autocreation

Disabled.