Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

i have a kvm host based on ubuntu 10.04 host , and the guest is rhel 5.3 64-bit,

on the guest i tried to execute mii-tool eth0

SIOCGMIIREG on eth0 failed: Input/output error
SIOCGMIIREG on eth0 failed: Input/output error
eth0: no autonegotiation, 100baseTx-FD, link ok

and mii-tool -v eth4

eth0: no autonegotiation, 100baseTx-FD, link ok
  product info: vendor 00:50:43, model 2 rev 0
  basic mode:   software reset, autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
  link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD

and mii-tool -r eth0 this is output /var/log/message

Feb 20 13:16:44 xil1 kernel: [ 1289.790780] e1000: eth4 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX

so that it is supposed to work with 1000MB/s but it still working with 100MB/s any suggestion what may be the problem ?

share|improve this question

Actually mii-tool will show you the ethernet cable speed that is connected to your system. But the capacity of ethernet card might be different.

so, you can see the capacity of your ethernet card by using lshw (listing hardware) command in linux (ubuntu).

You are seeing in 1000 in log because of it shows you interface card capacity that it can handle.

share|improve this answer
thanks for your help ,but the lshw aso show that "capacity: 1GB/s" the actual problem is not with mii-tool or whatever the problem is that the network speed can't work perfectly with 1GB/s ! any suggestions please ? – Moaz Refat Feb 20 '13 at 12:27
Your capacity will show only that your card is able to handle the packets that will come with the speed of 1GB/s. But for that your lan wire should be of 1000base/tx. – P4cK3tHuNt3R Feb 20 '13 at 12:35
it is because it is a guest kvm machine and its network speed is not perfect but the host is working perfect – Moaz Refat Feb 20 '13 at 12:56

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.