Port channels

The port channel is a powerful networking technology used to combine multiple physical Ethernet links into a single logical link. A basic port channel aggregates links from a single switch, while a multi-chassis port channel aggregates multiple physical links across a pair of switches, creating a single logical link.

A multi-chassis port channel creates redundancy for higher availability. You can configure one of the switches as active and the other as passive, then have the passive switch take over for the active switch when necessary.

Each port channel is identified a 10-bit number that is unique to the fabric. Every member link in a port channel is assigned the same identifier. This number is generated automatically, or you can specify the number when you create a port channel.

Guidelines for port channels

  • Nexus Hyperfabric supports Link Aggregation Control Protocol (LACP) — active.
  • The LACP timer rate is 3 times of 30 seconds.
  • Nexus Hyperfabric supports these port channel topologies:
    • Basic port channels, in which all physical links connect one device to another device.
    • Multi-chassis port channels, in which physical links across more than one switch are aggregated to connect to another device.
  • You can mix and match different supported switch models.

Limitations for port channels

  • A port channel's ID must be unique within the fabric.
  • All member ports of a port channel must have the same port speed and MTU.
  • A port channel supports a maximum of four member ports and spans a maximum of two switches. The switches can be either two leaf switches or two spine switches, but not a spine and a leaf switch.
  • A switch may act as a peer in more than one port channel only if the other peer switch is the same for each port channel.
  • You cannot mix different port channel pairs on the same switch.
  • If you have a Cisco UCS C-series rack server with a virtual interface card (VIC), link layer discovery protocol (LLDP) or link aggregation control protocol (LACP) might not work without enabling the Physical NIC Mode. However, if you enable the Physical NIC Mode, ensure that your server is using a Cisco IMC release that contains the fix for CSCwk79922. For basic information about LLDP and LACP, see the "Terminology" section of the Cisco Nexus Hyperfabric—Getting Started document.

Examples of supported and unsupported port channel topologies

Supported topologies
Supported topology: two port channels

This example shows two port channels:

  • PC1: Leaf1 and Leaf2
  • PC2: Leaf3 and Leaf4
Supported topology: four port channels

This example shows four port channels:

  • PC1: Leaf1 and Leaf2
  • PC2: Leaf1 and Leaf2
  • PC3: Leaf3 and Leaf4
  • PC4: Leaf3 and Leaf4
Supported topology: two port channels

This example shows two port channels:

  • PC1: Leaf1 and Leaf2
  • PC2: Leaf3 and Leaf4
Unsupported topologies
Unsupported topology: four aggregated leaf switches

A port channel spans a maximum of two leaf switches. In this example, four leaf switches are aggregated.
Unsupported topology: Leaf1 and Leaf2 are aggregated for one port channel, and Leaf1 and Leaf3 are aggregated for another

A leaf switch may act as a peer in more than one port channel only if the other peer switch is the same for each port channel. In this example, Leaf1 and Leaf2 are aggregated for one port channel, and Leaf1 and Leaf3 are aggregated for another.
Unsupported topology: a port channel with eight aggregated ports

A port channel supports a maximum of four member ports. In this example, the third port channel has eight aggregated ports.

Configure a port channel

A port must have the Unused role for you to be able to select it as member of a port channel. After you add a port channel, the role of the selected ports changes to Port channel and you cannot change the role in the port configuration page.

If you want to configure spanning tree protocol (STP) for the ports of a port channel, see the Configure logical networks document.

Follow these steps to configure a port channel.

Step 1

Select Fabrics, then select the desired fabric.

Step 2

If the fabric is not in the edit mode, select Switch to edit mode.

Step 3

In the Attachments area, select Port channel.

A table of existing port channels appears.

Port channel
Port channel

Step 4

Select + Add port channel and follow these substeps.

Add port channel
Add port channel

  1. For Port channel, enter an ID that is unique within the fabric.

    If you do not add an ID, Cisco Nexus Hyperfabric automatically generates one.

  2. For Switches, select one switch for a single-chassis port channel or two switches for a multi-chassis port channel.

  3. In the table of unused ports, select up to four ports.

    For a multi-chassis port channel, select ports from both switches.

  4. For Description, enter a description of the port channel.

  5. For Label, select Add, enter the text for the label, and press Enter.

  6. For Annotations, select Add and enter a key value pair.

Step 5

Select Save.

Finish and commit your changes

Your changes are not applied to the fabric until you review, commit, and push them.

 Note

For a more detailed description of this procedure, see "Workflow for making changes to the fabric" in Cisco Nexus Hyperfabric—Getting Started.

Follow these steps to finish and commit your changes.

Step 1

Select Review configuration.

Review configuration
Review configuration

Step 2

Verify your changes in the review list.

Step 3

Select Comment and push.

Step 4

In the Comment before pushing configuration dialog box, enter the reason for the change.

Step 5

Select Push configuration.

View port channel properties

You can view port channel properties such as member ports, link status, topology, labels, annotations, LACP status, and LACP counters.

Follow these steps to view port channel properties.

Step 1

Select Fabrics, then select the fabric whose properties you want to view.

Step 2

In the Attachments area, select Port channel.

A table of existing port channels appears.

The table shows this information for port channels:

  • Ports: Specifies the quantity of ports in the port channel.
  • Link state: An up arrow indicates that the links in the port channel are up, while a down arrow indicates that the links are down.
  • LACP status: An up arrow indicates that the ports are up and are operating as members of the port channel, while a down arrow indicates that one or more ports are operating as an individual ports and not as a members of the port channel.
  • Admin state: An up arrow indicates that the port channel is configured as enabled, while a down arrow indicates that the port channel is configured as disabled.
  • LACP: Specifies the LACP mode. Currently, Nexus Hyperfabric only supports the "active" mode.

The table shows this information for ports:

  • Link state: An up arrow indicates that the link is up, while a down arrow indicates that the link is down.
  • LACP status: An up arrow indicates that the port is up and is operating as a member of the port channel, while a down arrow indicates that the port is operating as an individual port and not as a member of the port channel.

Step 3

Expand a port channel to see the related ports and select the name of a port to view information about that port.

Port information
Port information

Step 4

While you are viewing the information about a port channel, you can select Edit port channel to edit that port channel.

Step 5

Select a port channel's name to view detailed information about that port channel, such as LACP status, link status, and switch status.

Port channel information
Port channel information