If you are wondering if your SFP module is recognized, try as root or sudo “ethtool –module-info eth0”. This should display the module type, characteristics, serial number, etc.
$ sudo ethtool -m eth0
Identifier : 0x03 (SFP)
Extended identifier : 0x04 (GBIC/SFP defined by 2-wire interface ID)
Connector : 0x07 (LC)
Transceiver codes : 0x00 0x00 0x00 0x01 0x00 0x00 0x00 0x00 0x00
Transceiver type : Ethernet: 1000BASE-SX
Encoding : 0x01 (8B/10B)
BR, Nominal : 1300MBd
Rate identifier : 0x00 (unspecified)
Length (SMF,km) : 0km
Length (SMF) : 0m
Length (50um) : 550m
Length (62.5um) : 270m
Length (Copper) : 0m
Length (OM3) : 0m
Laser wavelength : 850nm
Vendor name : CISCO-OEM
Vendor OUI : 00:00:00
Vendor PN : GLC-SX-MM-OSI
Vendor rev : 2.0
Option values : 0x00 0x1a
Option : RX_LOS implemented
Option : TX_FAULT implemented
Option : TX_DISABLE implemented
BR margin, max : 0%
BR margin, min : 0%
Vendor SN : ZZ201280353
Date code : 120128
Also, you can tell if the link is up using ethtool with no flags on the interface:
ethtool eth0
Settings for eth0:
Supported ports: [ FIBRE ]
Supported link modes: 1000baseX/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 1000baseX/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: 1000Mb/s
Duplex: Full
Port: FIBRE
PHYAD: 0
Transceiver: internal
Auto-negotiation: on
Cannot get wake-on-lan settings: Operation not permitted
Link detected: yes
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