Visualizar si un dispositivo tiene link

A menudo, es necesario verificar si un dispositivo tiene o no link, por ejemplo cuando pinchamos un cable en una tarjeta de red. Para ello, podemos usar el mandato entstat

Salida de ejemplo


 entstat -d ent3
-------------------------------------------------------------
ETHERNET STATISTICS (ent3) :
Device Type: Gigabit Ethernet-SX PCI-X Adapter (14106802)
Hardware Address: 00:02:55:33:ca:ff
Elapsed Time: 8 days 20 hours 10 minutes 20 seconds

Transmit Statistics:                          Receive Statistics:
--------------------                          -------------------
Packets: 3433434                              Packets: 12711676
Bytes: 8874830048                             Bytes: 9424162450
Interrupts: 0                                 Interrupts: 11286390
Transmit Errors: 0                            Receive Errors: 0
Packets Dropped: 0                            Packets Dropped: 0
                                              Bad Packets: 0
Max Packets on S/W Transmit Queue: 1
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 0

Broadcast Packets: 3469                       Broadcast Packets: 3851695
Multicast Packets: 9367                       Multicast Packets: 65934
No Carrier Sense: 0                           CRC Errors: 0
DMA Underrun: 0                               DMA Overrun: 0
Lost CTS Errors: 0                            Alignment Errors: 0
Max Collision Errors: 0                       No Resource Errors: 0
Late Collision Errors: 0                      Receive Collision Errors: 0
Deferred: 0                                   Packet Too Short Errors: 0
SQE Test: 0                                   Packet Too Long Errors: 0
Timeout Errors: 0                             Packets Discarded by Adapter: 0
Single Collision Count: 0                     Receiver Start Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 0

General Statistics:
-------------------
No mbuf Errors: 0
Adapter Reset Count: 0
Adapter Data Rate: 2000
Driver Flags: Up Broadcast Running
        Simplex 64BitSupport ChecksumOffload
        PrivateSegment LargeSend DataRateSet

Gigabit Ethernet-SX PCI-X Adapter (14106802) Specific Statistics:
-----------------------------------------------------------------
Link Status : Up
Media Speed Selected: Auto negotiation
Media Speed Running: 1000 Mbps Full Duplex
PCI Mode: PCI-X (100-133)
PCI Bus Width: 64-bit
Latency Timer: 144
Cache Line Size: 128
Jumbo Frames: Disabled
TCP Segmentation Offload: Enabled
TCP Segmentation Offload Packets Transmitted: 259702
TCP Segmentation Offload Packet Errors: 0
Transmit and Receive Flow Control Status: Enabled
XON Flow Control Packets Transmitted: 0
XON Flow Control Packets Received: 0
XOFF Flow Control Packets Transmitted: 0
XOFF Flow Control Packets Received: 0
Transmit and Receive Flow Control Threshold (High): 49152
Transmit and Receive Flow Control Threshold (Low): 24576
Transmit and Receive Storage Allocation (TX/RX): 8/56