We're running ubuntu 18.04, with the following configuration of netplan:

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: yes

Currently we're running into an issue with DHCP, seems old IPs are not being freed after assigning a new one:

2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:1a:4a:X:Y:Z brd ff:ff:ff:ff:ff:ff
    inet 10.X.Y.175/23 brd 10.X.Y.255 scope global ens3
       valid_lft forever preferred_lft forever
    inet 10.X.Y.201/23 brd 10.X.Y.255 scope global secondary dynamic ens3
       valid_lft 3136sec preferred_lft 3136sec
    inet 10.X.Y.168/23 brd 10.X.Y.255 scope global secondary ens3
       valid_lft forever preferred_lft forever
    inet6 fe80::21a:4aff:fe97:5f31/64 scope link 
       valid_lft forever preferred_lft forever

This is generating duplicated IP addresses as some IPs are being reused but not freed, generating to the users a lot of issues.

What is causing this behavior and how can it be solved?

  • This is happening only on Ubuntu 18.04. We have thousands of VMs with other OSs like Ubuntu 14.04, CentOS, RedHat and it won't happen here. – nKn Oct 10 at 13:13

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