Score:1

no dhcp ipv4 after upgrading to 20.04.3, other 18.04 works

cn flag

Got a server install of Ubuntu 20.04.2 server. After updating to 20.04.3, it no longer gets a dhcpv4 lease. Netplan has the correct the interface. Doesn't seem like there's much I can check... Only ipv6 works. Other information: Other installs of ubuntu 18.04 and centos and windows all get dhcp correctly. This issue is now happening on multiple ubuntu 20.04.3 installs of various configurations after recent updates. Unfortunately not enough info to pindown which package might have broken it, but it's within the past 3 month.

iptables:

iptables screenshot

netplan:

netplan screenshot

ip addr result:

ip addr result screenshot

waltinator avatar
it flag
Look at the logs! `sudo journalctl -b 0 -u NetworkManager`. Read `man journalctl`.
cn flag
journalctl -t dhclient just shows a bunch of DHCPDISCOVER on eth0 to 255.255.255.255 port 67 with no reply. Note that ubuntu 18.04 on the same network are all working fine so it's not a server issue. Purely client side and only on 20.04.3.
Terrance avatar
id flag
It may not be eth0, it may be a predictive name instead. What is the output of `ip addr`? Please add the output to your question.
cn flag
Unfortunately it is eth0. added ipaddr and iptables for good measure.
Terrance avatar
id flag
I think you may be missing the renderer as well. Unfortunately, I don't use netplan because I am an old school guy, but looking at the site for netplan it shows to use one: https://netplan.io/
cn flag
netplan defaults to networkd for a server install. journalctl already shows dhclient is running. just not getting a DHCPOFFER.
Terrance avatar
id flag
Everything I am looking at shows a renderer line. What do you have to lose by adding a line to your configuration? https://netplan.io/examples/ The first link though does say that networkd doesn't bring it up automatically. "Using networkd as a renderer does not let devices automatically come up using DHCP; each interface needs to be specified in a file in /etc/netplan for its configuration to be written and for it to be used in networkd."
cn flag
Added renderer: networkd line and did netplan apply but no change. But yes, eth0 is specified in the file so it should be bringing it up. But it's not. :(
Terrance avatar
id flag
UGH! Unfortunately, I am out of ideas. +1 to help you on your way with visibility! I hope that someone may have experienced it and can help you solve the issue. If you can, try editing your question and using the `{}` for code and do copy and paste instead of images. Thanks!
Terrance avatar
id flag
Sorry, one more thing to try then I am out of ideas completely. Try running `sudo dhclient -r eth0` then `sudo dhclient eth0` and see if it picks up an IP address.
ru flag
Just a question, but is this a VM/Container? I ask because `eth0` is the very old legacy way of doing ethernet device naming, and if this is a VM or Container something may be screwy on the host system making there be connection issues.
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