[libvirt-users] Automatically assign static ipv4 via dhcp to new VMs

[Tim]

Thanks for the hint with net-update, thats exactly that what I was
looking for.

Am 07.10.2013 13:10, schrieb Laine Stump:
> On 10/04/2013 12:09 PM, Tim wrote:
>> Hi guys,
>>
>> I'm running a KVM/libvirt host in a datacenter and got a fancy IPv4
>> subnet from my provider. I'm able to assign IPs from that subnet via
>> dhcp to my VMs:
>>
>> host01 ~ # virsh net-dumpxml internet
>> <network connections='3'>
>>   <name>internet</name>
>>   <uuid>37b888cc-510f-46f1-9246-346da96222ed</uuid>
>>   <forward dev='enp5s0f0' mode='route'>
>>     <interface dev='enp5s0f0'/>
>>   </forward>
>>   <bridge name='virbr1' stp='on' delay='0'/>
>>   <mac address='52:54:00:13:39:d5'/>
>>   <ip address='XX.YY.253.2' netmask='255.255.255.224'>
>>     <dhcp>
>>       <range start='XX.YY.253.4' end='XX.YY.253.30'/>
>>       <bootp file='pxelinux.0' server='XX.YY.99.100'/>
>>     </dhcp>
>>   </ip>
>> </network>
>>
>>
>>
>> What I would like to do:
>>
>> 1) Right know it seems like dnsmasq assigns ip-addresses randomly to
>> VMs, is there any way to assign them in ascending order?
> 
> Whene there is no <host> entry for a particular mac address, dnsmasq
> decides on the IP address to assign to each client based on some sort of
> hash of the mac address (and maybe some other info). This makes it as
> stable as possible without requiring user intervention.
> 
>>
>> 2) IPs are not statically assigned. Is it possible to add something like
>> this automatically at the first VM-start to the xml definition?:
>> <host mac='AA:BB:CC:DD:EE:FF' ip='192.168.122.2' name='foobar'/>
> 
> That is exactly what needs to be added to the <dhcp> section of the
> libvirt network *just before* starting the guest for the first time. If
> you add it using "virsh net-edit", you will have to net-destroy then
> net-start the network in order for it to take effect though, and that
> disconnects all current guests from the network, which you certainly
> don't want.
> 
> Fortunately, in libvirt 0.10.0 and later (I think that is the version it
> was added) you can use the "virsh net-update" command to add net static
> host entries immediately without restarting the network; something like
> this:
> 
>   virsh net-update MyGuest --live internet add \
>     ip-dhcp-host "<host mac='AA:BB:CC:DD:EE:FF' ip='192.168.122.2'
> name='foobar'/>"
>