Looks like the ex4600 uses the QFX layer two commands.
And the bad news is:
- You cannot set the speed on these interfaces.
Configuring the Link Settings for Gigabit Ethernet Interfaces on QFX5100-48S, QFX5100-24Q Switches, and EX4600 Switches
Devices include a factory default configuration that enables Gigabit Ethernet interfaces with applicable link settings.
The following default configurations are available on Gigabit Ethernet interfaces:
- You cannot set the speed on these interfaces.