This article provides confirmation that the configuration under the set interfaces <interface-name> speed hierarchy in M320 Series devices has been removed in Junos OS release 15.1, making speed unconfigurable.

Customers may encounter a syntax error as shown below when they attempt to configure speed settings in M320.

user@R1> edit
Entering configuration mode
 
[edit]
user@R1# set interfaces ge-1/0/0 sp
                                 ^
syntax error.
user@R1# set interfaces ge-1/0/0 sp

In Junos OS release 13.3, speed is configurable and can be set to 100mbps as shown below:

user@R1> show version brief
Hostname: R1
Model: m320
Junos: 13.3R1.2
JUNOS Base OS boot [13.3R1.2]
JUNOS Base OS Software Suite [13.3R1.2]
---trimmed---
JUNOS py-base-i386 [13.3R1.2]          
 
user@R1> show interfaces ge-4/1/0 extensive |match speed   
  Link-level type: Ethernet, MTU: 1514, MRU: 0, Speed: 100mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled

However, it is removed in Junos OS release 15.1.

[edit]
user@R1# set interfaces ge-1/0/0 sp
                                 ^
syntax error.
user@R1# set interfaces ge-1/0/0 sp

user@R1> show version brief
Hostname: R1
Model: m320
Junos: 15.1R6.7
JUNOS Base OS boot [15.1R6.7]
JUNOS Base OS Software Suite [15.1R6.7]
---trimmed---
JUNOS Routing Software Suite [15.1R6.7]
 
user@R1> show interfaces ge-4/1/0 extensive |match speed   
  Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Speed: 1000mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled,

There is no workaround available for the above because the M320 device and software code are End of Engineering and End of Support.