This document explains how to configure a 100G QSFP28 port on an M4350 switch to operate in breakout mode, allowing it to function as four individual 10G interfaces.
Configuring a 100G port in breakout mode enables connectivity to multiple 10G devices using a single QSFP28 uplink port.
If all supported 100G ports are configured in breakout mode, the switch can provide up to 16 additional 10G interfaces (model dependent).
Requirements:
The following components are required:
- 100G QSFP28 transceiver (Single Mode or Multimode)
- FLEXOPTIX:
- Optic.ca:
- MPO/MTP to 4×LC breakout cable (Single Mode or Multimode)
- FLEXOPTIX:
- Optic.ca:
- 10G SFP+ transceivers (Single Mode or Multimode)
- NETGEAR:
- Single-mode: AXM762
- Multi-mode: AXM761
- NETGEAR:
Configure a 100G port in breakout mode
Configuration methods:
You can configure a breakout using either:
- The Web Interface (Main UI)
- The CLI
Method 1: Web interface (Main UI)
- Open a web browser and connect to the switch using its management IP address.
- Log in using administrator credentials.
- Click Main UI Login.
- Navigate to: Switching > Ports > Expandable Port Configuration.
- Select the 100G port you want to configure.
- Change the Port Mode to 4x25G.
- Click the Apply button.
Note: The “Expanded Interfaces” displays after applying this setting. These are the logical ports created by breakout mode and must be configured in the next step. - Navigate to: Switching > Ports > Port Configuration
- Select the expanded interface range (for example: 1/0/53–1/0/56).
- Configure the following:
- Speed: 10G
- Auto-Negotiation: Disabled
- Click Apply.
After configuration, the interfaces show a link at 10G if connected properly.
Click the Save button (top-right corner) to ensure the configuration persists after reboot.
Method 2: CLI configuration
Connect to the switch.
Access the switch through one of the following options:
- Console
- SSH
- Telnet
Enter privileged mode:
> enable
# configure
Configure breakout mode on the 100G port.
Enter interface configuration:
(config)# interface 1/0/43
Enable breakout:
(interface 1/0/43)# hardware profile portmode 4x25G
Verify breakout interfaces.
Check the generated breakout interfaces:
(interface 1/0/43)# show interfaces hardware profile 1/0/43
Example output:
Interface Mode Operating Expanded Interfaces
1/0/43 4x25G 4x25G 1/0/53-1/0/56
2x50G 1/0/65-1/0/66
Note: The “expanded interfaces” are the logical 25G ports created from the original 100G interface.
Configure the breakout ports for 10G operation.
Enter the expanded interface range:
(config)# interface 1/0/53-1/0/56
Disable auto-negotiation:
(Interface)# no auto-negotiate
Set the speed and duplex:
(Interface)# speed 10G full-duplex
Save the configuration.
Exit configuration mode and save:
# end
# save
Y
Important Notes:
- Breakout mode converts a 100G QSFP28 port into four 25G logical interfaces.
- When connecting to 10G devices, you must set the speed to 10G.
- Disable auto-negotiation when connecting to fixed-speed 10G devices.
- Only specific ports support breakout mode. Refer to the hardware datasheet for model-specific limitations.