On SRX300-series device, one or more 1GbE interfaces may remain down even though the connected SFP module is detected correctly and valid optical signal is received from the peer device.

The affected interface is administratively enabled but remains in a Physical link is Down state.

Example:
user@srx> show interfaces ge-0/0/7
 
Physical interface: ge-0/0/7, Enabled, Physical link is Down
...
Device flags : Present Running Down
Interface flags: Hardware-Down
...
Active alarms : LINK
Active defects : LINK

Optical diagnostics show that:

-> The SFP is detected correctly.
-> Transmit and receive optical power levels are within acceptable thresholds.
-> No optical alarms or warnings are present.
-> Valid light is being received from the remote device.

Example:
user@srx> show interfaces diagnostics optics ge-0/0/7
 
Laser receiver power : -9.15 dBm
Laser rx power low alarm : Off
Laser rx power high alarm : Off
...

When optical connectivity is healthy but the interface remains down, the issue is often related to Ethernet link establishment or auto-negotiation between the connected devices.

Resolution/ Workaround:

-> Verify the speed and duplex settings on both ends of the link.
-> Confirm that the interface configurations are compatible between the local and remote devices.
-> Toggle or re-enable auto-negotiation on the peer device, if supported.
-> Recheck the interface status after the negotiation settings are applied.