[Bug 1776013] Re: systemd-networkd: DHCP lease lost (Ubuntu 18.04)

[Nagarjuna Manchineni]

Hi All,

I know the issue is closed. However, I am observing this issue. I am on
a network where the DHCP lease time out occurs every 24 hours and
whenever that happens my network gets restarted. Due to this I am
loosing some of my IP route entries which in turn causes failures to my
application.

I have tried multiple workarounds like the one that has been suggested
above (critical connection). However, none of them helped in resolving
the issue. Currently I moved from Ubuntu 18.04 to Ubuntu 16.04
temporarily.

If someone who already has a solution or any pointers that could resolve
this network restart issue that would be helpful to others like me.

TIA!

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https://bugs.launchpad.net/bugs/1776013

Title:
  systemd-networkd: DHCP lease lost (Ubuntu 18.04)

Status in systemd package in Ubuntu:
  Invalid

Bug description:
  I have a Linux router whose external Ethernet interface is configured from ISP's DHCP server.
  After its migration from Ubuntu 16.04 + ifupdown + isc-dhcp-client to Ubuntu 18.04 + netplan.io + systemd-networkd, I noticed that systemd-networkd plays overly fairly when it can not get a timely renew response from ISP's DHCP server: it honestly removes the dynamic IP from the interface and restores (often the same) IP only when ISP's DHCP server gives it a proper response again. Which causes 1..5-minute pauses in Internet availability since my ISP's DHCP server is for some reason flaky, i.e. it can become unresponsive for some periods of time. I never noticed this problem with isc-dhcp-client, and started noticing it only after migrating DHCP client role to systemd-networkd.
  The question is, can I (or you) make systemd-networkd DHCP client behave more relaxedly ?
  I know that most DHCP clients (isc-, pump, dhcpcd) at some stage of their development decided to implement such relaxed logic, i.e. to keep last-configured dynamic IP on the interface despite the lack of responses from DHCP server. As this is easier to implement than to make ISP staff fix their services, I would suppose there should be some knob in systemd-networkd settings. Or, at least, an idea to implement something similar in the future.

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