Why do KVM guests show vnet interface link speed as 10Mbps

Solution Verified - Updated -

Issue

  • ethtool reports speed of a vnet interface as 10Mbps on KVM guest machine.
# ethtool vnet1
Settings for vnet1:  
 Supported ports: [ ]  
 Supported link modes:  
 Supports auto-negotiation: No  
 Advertised link modes:  Not reported  
 Advertised pause frame use: No  
 Advertised auto-negotiation: No  
 Speed: 10Mb/s   
 Duplex: Full  
 Port: Twisted Pair  
 PHYAD: 0  
 Transceiver: internal  
 Auto-negotiation: off  
 MDI-X: Unknown  
 Current message level: 0xffffffa1 (-95)  
 Link detected: yes

Environment

  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Virtualization 3 Hypervisors
  • Red Hat Virtualization 4 Hypervisors
  • KVM based Virtual Machines

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