Juniper JUNOSE 10.0.X PHYSICAL LAYER Configuration Manual page 226

JUNOSe 10.0.x Physical Layer Configuration Guide
mtu
speed
NOTE: If you set either the line speed or duplex mode to automatically negotiate by
using the automatically negotiate keyword, the router negotiates both parameters.
You can specify different values to prevent the router from negotiating these
parameters.
Automatic negotiation is not supported for the FE-8 SFP I/O module. For this I/O
module, the default speed is 100 Mbps.
200
Configuring the Physical Interface
The default value is 300 seconds.
Example
host1(config-if)#load-interval 90
Use the no version to restore the default time interval, 300 seconds.
See load-interval.
Use to specify the MTU for an interface.
Specify a value in the range 64–9188 bytes. The range for FE-8 I/O modules is
64–9042 bytes.
This command does not work for the Fast Ethernet port on the SRP module.
Example
host1(config-if)#mtu 9000
Use the no version to specify the default, 1518.
See mtu.
Use to specify the line speed.
This command also works on the Fast Ethernet port on the SRP module on all
E-series routers. For more information, see JUNOSe System Basics Configuration
Guide.
Example
host1(config-if)#speed 10
Use the no version to revert to the default, either automatically negotiate or 100
Mbps (FE-8 SFP I/O module only).
See speed.