Gigabit Ethernet adapter problem

[Matthew Seaman]

On 31/10/2017 15:24, Ernie Luzar wrote:
> 
> em - Intel(R) PRO/1000 Gigabit Ethernet adapter driver
> 
> The boot messages show the Gigabit Ethernet adapter is correctly
> identified at boot time as shown below.
> 
> em0: <Intel(R) PRO/1000 Network Connection 7.6.1-k> port 0xf080-0xf09f
>      mem 0xf7d00000-0xf7d1ffff,0xf7d3c000-0xf7d3cfff irq 20 at
>      device 25.0 on pci0
> em0: Using an MSI interrupt
> em0: Ethernet address: d0:50:99:93:75:98
> em0: netmap queues/slots: TX 1/1024, RX 1/1024
> 
> 
> But after the system is up and running ifconfig em0 shows
> 
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>
>         metric 0 mtu 1500
>     options=4019b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,
>         TSO4,VLAN_HWTSO>
>     ether d0:50:99:93:75:98
>     hwaddr d0:50:99:93:75:98
>     inet 10.0.10.2 netmask 0xff000000 broadcast 10.255.255.255
>     nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
>     media: Ethernet autoselect (100baseTX <full-duplex>)
>     status: active
> 
> and we see that (100baseTX <full-duplex>) has been selected as default
> and it should be (1000baseTX <full-duplex>).
> 
> How do I force the Ethernet adapter into Gigabit mode?

This sort of down-grade is either because the switch port you've go the
machine plugged into is somehow set to negotiate to 100Mb/s, or else
you've got some dodgy cabling and consequently the system has backed off
to 100Mb/s because it can't sustain 1000Mb/s.

Try looking at the output of 'netstat -i' -- if there are any errors
listed in the ierrs or oerrs columns, and particularly if they are
increasing over time.  That indicates some sort of hardware problem,
usually due to a network cable having broken or been kinked or even tied
too tightly into a bundle.  Start by swapping out the ethernet cable --
it's cheap to replace.

	Cheers,

	Matthew