Gigabit Ethernet adapter problem
Kent Kuriyama
kent.kuriyama at gmail.com
Tue Oct 31 17:05:43 UTC 2017
I had the same problem in which a supposedly GigE connection would
negotiate down to 100 Mbs. The problem as a bad NIC on my side. I have
also seen 100 Mbs speeds when the jumper cable that I used was not up to
par.
On Tue, Oct 31, 2017 at 5:43 AM, Matthew Seaman <
m.seaman at infracaninophile.co.uk> wrote:
> 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
>
>
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