How to change libvirt DHCP lease time

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1

I’m using KVM via Qemu via libvirt with Fedora 30 for the host machine. I find that a VM connected via NAT requests DHCP request about every 20~25 minutes, and I want to change the DHCP lease (or request?) time longer.

My problem is exactly the same as the one mentioned here https://stackoverflow.com/questions/40309451/how-to-change-libvirt-dhcp-lease-time

A patch for this feature has been requested here https://www.redhat.com/archives/libvir-list/2016-October/msg00561.html Can someone please tell me the status of that patch request? That’s not something I know how to do yet.

In case anyone is wondering why am I duplicating question here. It’s because I’m hoping the Fedora community would be more helpful than stackoverflow community.

2

It is not merged with the master and not supported in Fedora 30.

Possible solutions:

  • Static address.
  • External DHCP server with bridging or macvtap.
  • Custom DHCP instance instead of the default one.
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3

@vgaetera Hello,

I tried making the IP address of the virtual machine static but it’s still not working.

Sep 16 23:31:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPDISCOVER(virbr1) 192.168.122.248 52:54:00:55:23:80
Sep 16 23:31:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPOFFER(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 16 23:31:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPREQUEST(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 16 23:31:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPACK(virbr1) 192.168.1.128 52:54:00:55:23:80 win2k19
Sep 17 00:01:09 localhost.localdomain dnsmasq-dhcp[1918]: DHCPREQUEST(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 17 00:01:09 localhost.localdomain dnsmasq-dhcp[1918]: DHCPACK(virbr1) 192.168.1.128 52:54:00:55:23:80 win2k19
Sep 17 00:28:32 localhost.localdomain dnsmasq-dhcp[1918]: DHCPREQUEST(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 17 00:28:32 localhost.localdomain dnsmasq-dhcp[1918]: DHCPACK(virbr1) 192.168.1.128 52:54:00:55:23:80 win2k19
Sep 17 00:56:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPREQUEST(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 17 00:56:10 localhost.localdomain dnsmasq-dhcp[1918]: DHCPACK(virbr1) 192.168.1.128 52:54:00:55:23:80 win2k19
Sep 17 01:23:04 localhost.localdomain dnsmasq-dhcp[1918]: DHCPREQUEST(virbr1) 192.168.1.128 52:54:00:55:23:80
Sep 17 01:23:04 localhost.localdomain dnsmasq-dhcp[1918]: DHCPACK(virbr1) 192.168.1.128 52:54:00:55:23:80 win2k19

The instructions I used for setting the IP address of the virtual machine to static is https://www.cyberciti.biz/faq/linux-kvm-libvirt-dnsmasq-dhcp-static-ip-address-configuration-for-guest-os/

Doing “sudo virsh net-list” gives me,

 Name       State    Autostart   Persistent
---------------------------------------------
 default    active   yes         yes
 ProxyARP   active   yes         yes

Doing “sudo virsh net-dumpxml ProxyARP” gives me,

<network>
  <name>ProxyARP</name>
  <uuid>7f378b15-ad13-420e-a317-3465ef2841e0</uuid>
  <forward dev='wlp3s0' mode='route'>
    <interface dev='wlp3s0'/>
  </forward>
  <bridge name='virbr1' stp='on' delay='0'/>
  <mac address='52:54:00:cd:39:17'/>
  <domain name='ProxyARP'/>
  <ip address='192.168.1.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.1.128' end='192.168.1.254'/>
      <host mac='52:54:00:55:23:80' name='win2k19' ip='192.168.1.128'/>
    </dhcp>
  </ip>
</network>

The network segment of the virtual machines XML dump from doing “sudo virsh dumpxml win2k19” is,

<interface type='network'>
  <mac address='52:54:00:55:23:80'/>
  <source network='ProxyARP'/>
  <model type='e1000e'/>
  <address type='pci' domain='0x0000' bus='0x0b' slot='0x00' function='0x0'/>
</interface>
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4

I mean that you can completely disable DHCP or just ignore it and configure a static IP address in the VM.