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Totally new to KVM here, so maybe there is nothing wrong with my set up, but I am running 10 guest VMs on my Ubuntu 12.04 server via KVM and I just noticed that ifconfig returned a plethora of interfaces.

It looks like there is one of these for each guest:

vnet5     Link encap:Ethernet  HWaddr fe:54:00:51:e8:66  
          inet6 addr: fe80::fc54:ff:fe51:e866/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1707 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2506 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:1850605 (1.8 MB)  TX bytes:375034 (375.0 KB)

Does this seem right? It strikes me that I have something misconfigured somewhere.

What are these anyway?

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1 Answer 1

up vote 2 down vote accepted

It's not one vnet for each guest but one vnet for each network adapter in a VM. You can configure the vnet numbers but usually they are not relevant. The vnet interfaces are bridged to either a physical or a logical (host-only) interface.

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So there's no getting rid of them or combining them? Its not a configuration mistake then? –  hdave Mar 14 '13 at 12:32
    
The only thing you can change in configuration is the number of each vnet. Have a look at brctl show. Take away the interface and the connectivity is gone. In fact if you take down a private network via virsh and bring it up again then libvirt forgets to restore the bridging. You can repeair that manually with brctl. I think this level of transparency is great. –  Hauke Laging Mar 14 '13 at 13:05

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