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My operating system is Ubuntu 12.04. My cable modem is a motorola surfboard extreme. My comcast cable is 58 mbps. I'm using a belkin router. And my NIC is a NVIDIA Corporation MCP51 Ethernet Controller (rev a3).

The problem I have is I only get 100 mb/s speed:

$ sudo ethtool eth0
[sudo] password for myuser: 
Settings for eth0:
    Supported ports: [ MII ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes:  100baseT/Full 
    Advertised pause frame use: No
    Advertised auto-negotiation: Yes
    Speed: 100Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 1
    Transceiver: external
    Auto-negotiation: on
    Supports Wake-on: g
    Wake-on: d
    Link detected: yes

When I try to switch speed to 1000, I lose network connection instantly:

$ sudo ethtool -s eth0 speed 1000 duplex full
$ sudo ethtool eth0
Settings for eth0:
    Supported ports: [ MII ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes:  1000baseT/Full 
    Advertised pause frame use: No
    Advertised auto-negotiation: Yes
    Speed: Unknown!
    Duplex: Unknown! (255)
    Port: MII
    PHYAD: 1
    Transceiver: external
    Auto-negotiation: on
    Supports Wake-on: g
    Wake-on: d
    Link detected: no

I am forced to change it back to 100 to get network connection back. What is causing this issue?

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  • Note, 1 gigabyte is 8192 mb. You're not going to get 1 GB/s on an internet connection with Comcast. Also note that you are attempting to increase your connection to the modem from 100mb/s to 1000mb/s when your internet connection is 58mb/s. This will not increase your throughput on the internet, only your throughput to other devices connected to the same network. That said, what happens when you let it auto-negotiate? It should choose the fastest based on the link rate supplied to it. The only factors here are the modem port (which supports 1000), your card (which supports 1000) and the cable.
    – MaQleod
    Apr 1, 2014 at 15:12
  • Which Belkin router model, exactly? Are you sure its LAN ports are gigabit? Does your Ethernet cable have 4 pairs (8 wires) of Cat5 or better cable? Are the right pairs of pins paired in a twisted pair of cable (e.g. pins 3 & 6 must be a pair, and pins 4 & 5 must be a pair; not "3 & 4" and "5 & 6").
    – Spiff
    Apr 1, 2014 at 21:44

1 Answer 1

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First thing to try is another ethernet cable. Some are only capable of 100mbps.

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