Strange network problem with Proxmox 7.1-6 and Debian 11

S

SomeUser

Member
Aug 1, 2020
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Just received a Dell R520, and did a fresh install of Proxmox. Added Debian 10 (buster) guest. No issues with networking. Installed Debian 11 (bullseye). When I run a "/etc/init.d/networking restart" the networking bits stop working.

This is the "Before" running /etc/init.d/networking restart

/etc/network/interfaces
Code: 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug ens18
iface ens18 inet dhcp

$ ip a
Code: 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether ae:3c:d9:36:a2:7b brd ff:ff:ff:ff:ff:ff
    altname enp0s18
    inet 10.11.12.163/24 brd 10.11.12.255 scope global ens18
       valid_lft forever preferred_lft forever
   inet 10.11.12.109/24 brd 10.11.12.255 scope global secondary dynamic ens18
      valid_lft 85543sec preferred_lft 85543sec
   inet6 fe80::ac3c:d9ff:fe36:a27b/64 scope link
      valid_lft forever preferred_lft forever

$ ip route
Code: 
default via 10.11.12.1 dev ens18
10.11.12.0/24 dev ens18 proto kernel scope link src 10.11.12.163
10.11.12.1 dev ens18 scope link

When I run a "/etc/init.d/networking restart", the network dies. "ip a" and "ip route" gives me the following - yes, blank route:

This is the "After" running /etc/init.d/networking restart.

Code: 
root@debian11dhcp:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens18: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether ae:3c:d9:36:a2:7b brd ff:ff:ff:ff:ff:ff
    altname enp0s18
root@debian11dhcp:~# ip route
root@debian11dhcp:~#

/var/log/syslog has the following:
Code: 
Nov 27 23:46:57 debian11dhcp systemd[1]: Stopping Raise network interfaces...
Nov 27 23:46:57 debian11dhcp dhclient[726]: Killed old client process
Nov 27 23:46:57 debian11dhcp ifdown[726]: Killed old client process
Nov 27 23:46:58 debian11dhcp dhclient[726]: Internet Systems Consortium DHCP Client 4.4.1
Nov 27 23:46:58 debian11dhcp ifdown[726]: Internet Systems Consortium DHCP Client 4.4.1
Nov 27 23:46:58 debian11dhcp ifdown[726]: Copyright 2004-2018 Internet Systems Consortium.
Nov 27 23:46:58 debian11dhcp ifdown[726]: All rights reserved.
Nov 27 23:46:58 debian11dhcp ifdown[726]: For info, please visit https://www.isc.org/software/dhcp/
Nov 27 23:46:58 debian11dhcp dhclient[726]: Copyright 2004-2018 Internet Systems Consortium.
Nov 27 23:46:58 debian11dhcp dhclient[726]: All rights reserved.
Nov 27 23:46:58 debian11dhcp dhclient[726]: For info, please visit https://www.isc.org/software/dhcp/
Nov 27 23:46:58 debian11dhcp dhclient[726]:
Nov 27 23:46:58 debian11dhcp dhclient[726]: Listening on LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Listening on LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Sending on   LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Sending on   Socket/fallback
Nov 27 23:46:58 debian11dhcp dhclient[726]: Sending on   LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp dhclient[726]: Sending on   Socket/fallback
Nov 27 23:46:58 debian11dhcp dhclient[726]: DHCPRELEASE of 10.11.12.109 on ens18 to 10.11.12.2 port 67
Nov 27 23:46:58 debian11dhcp ifdown[726]: DHCPRELEASE of 10.11.12.109 on ens18 to 10.11.12.2 port 67
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} address 10.11.12.109/24 label ens18
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for 10.11.12.109 on ens18.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} address 10.11.12.163/24 label ens18
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for 10.11.12.163 on ens18.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Leaving mDNS multicast group on interface ens18.IPv4 with address 10.11.12.163.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} route 10.11.12.0 gw 0.0.0.0 scope 253 <LINK>
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Interface ens18.IPv4 no longer relevant for mDNS.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {RX} 5105 packets 1464831 bytes
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {TX} 1390 packets 139445 bytes
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {update} flags 4098 <DOWN>
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Interface ens18.IPv6 no longer relevant for mDNS.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Leaving mDNS multicast group on interface ens18.IPv6 with address fe80::ac3c:d9ff:fe36:a27b.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for fe80::ac3c:d9ff:fe36:a27b on ens18.
Nov 27 23:46:59 debian11dhcp systemd[1]: networking.service: Succeeded.
Nov 27 23:46:59 debian11dhcp systemd[1]: Stopped Raise network interfaces.
Nov 27 23:46:59 debian11dhcp systemd[1]: Starting Raise network interfaces...
Nov 27 23:46:59 debian11dhcp systemd[1]: Finished Raise network interfaces.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {newlink} index 2 address AE:3C:D9:36:A2:7B mtu 1500
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {newlink} index 2 operstate 2 <DOWN>
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} route fe80:: gw :: scope 0 <UNIVERSE>

journalctl gives the following:
Code: 
Nov 27 23:46:57 debian11dhcp systemd[1]: Stopping Raise network interfaces...
Nov 27 23:46:57 debian11dhcp dhclient[726]: Killed old client process
Nov 27 23:46:57 debian11dhcp ifdown[726]: Killed old client process
Nov 27 23:46:58 debian11dhcp dhclient[726]: Internet Systems Consortium DHCP Client 4.4.1
Nov 27 23:46:58 debian11dhcp ifdown[726]: Internet Systems Consortium DHCP Client 4.4.1
Nov 27 23:46:58 debian11dhcp ifdown[726]: Copyright 2004-2018 Internet Systems Consortium.
Nov 27 23:46:58 debian11dhcp ifdown[726]: All rights reserved.
Nov 27 23:46:58 debian11dhcp ifdown[726]: For info, please visit https://www.isc.org/software/dhcp/
Nov 27 23:46:58 debian11dhcp dhclient[726]: Copyright 2004-2018 Internet Systems Consortium.
Nov 27 23:46:58 debian11dhcp dhclient[726]: All rights reserved.
Nov 27 23:46:58 debian11dhcp dhclient[726]: For info, please visit https://www.isc.org/software/dhcp/
Nov 27 23:46:58 debian11dhcp dhclient[726]:
Nov 27 23:46:58 debian11dhcp dhclient[726]: Listening on LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Listening on LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Sending on   LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp ifdown[726]: Sending on   Socket/fallback
Nov 27 23:46:58 debian11dhcp dhclient[726]: Sending on   LPF/ens18/ae:3c:d9:36:a2:7b
Nov 27 23:46:58 debian11dhcp dhclient[726]: Sending on   Socket/fallback
Nov 27 23:46:58 debian11dhcp dhclient[726]: DHCPRELEASE of 10.11.12.109 on ens18 to 10.11.12.2 port 67
Nov 27 23:46:58 debian11dhcp ifdown[726]: DHCPRELEASE of 10.11.12.109 on ens18 to 10.11.12.2 port 67
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} address 10.11.12.109/24 label ens18
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for 10.11.12.109 on ens18.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} address 10.11.12.163/24 label ens18
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for 10.11.12.163 on ens18.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Leaving mDNS multicast group on interface ens18.IPv4 with address 10.11.12.163.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} route 10.11.12.0 gw 0.0.0.0 scope 253 <LINK>
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Interface ens18.IPv4 no longer relevant for mDNS.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {RX} 5105 packets 1464831 bytes
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {TX} 1390 packets 139445 bytes
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {update} flags 4098 <DOWN>
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Interface ens18.IPv6 no longer relevant for mDNS.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Leaving mDNS multicast group on interface ens18.IPv6 with address fe80::ac3c:d9ff:fe36:a27b.
Nov 27 23:46:59 debian11dhcp avahi-daemon[366]: Withdrawing address record for fe80::ac3c:d9ff:fe36:a27b on ens18.
Nov 27 23:46:59 debian11dhcp systemd[1]: networking.service: Succeeded.
Nov 27 23:46:59 debian11dhcp systemd[1]: Stopped Raise network interfaces.
Nov 27 23:46:59 debian11dhcp systemd[1]: Starting Raise network interfaces...
Nov 27 23:46:59 debian11dhcp systemd[1]: Finished Raise network interfaces.
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {newlink} index 2 address AE:3C:D9:36:A2:7B mtu 1500
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {newlink} index 2 operstate 2 <DOWN>
Nov 27 23:46:59 debian11dhcp connmand[371]: ens18 {del} route fe80:: gw :: scope 0 <UNIVERSE>

If I were to run "dhclient ens18", it does get an IP address and the network is available again. Obviously this is suboptimal... syslog gives the following entries then:
Code: 
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {RX} 5105 packets 1464831 bytes
Nov 28 00:22:17 debian11dhcp kernel: [ 3533.011024] 8021q: adding VLAN 0 to HW filter on device ens18
Nov 28 00:22:17 debian11dhcp kernel: [ 3533.012942] e1000: ens18 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
Nov 28 00:22:17 debian11dhcp kernel: [ 3533.015868] IPv6: ADDRCONF(NETDEV_CHANGE): ens18: link becomes ready
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {TX} 1390 packets 139445 bytes
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {update} flags 4099 <UP>
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {newlink} index 2 address AE:3C:D9:36:A2:7B mtu 1500
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {newlink} index 2 operstate 2 <DOWN>
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {add} route fe80:: gw :: scope 0 <UNIVERSE>
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {RX} 5105 packets 1464831 bytes
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {TX} 1390 packets 139445 bytes
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {update} flags 69699 <UP,RUNNING,LOWER_UP>
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {newlink} index 2 address AE:3C:D9:36:A2:7B mtu 1500
Nov 28 00:22:17 debian11dhcp connmand[371]: ens18 {newlink} index 2 operstate 6 <UP>
Nov 28 00:22:17 debian11dhcp dhclient[834]: DHCPREQUEST for 10.11.12.163 on ens18 to 255.255.255.255 port 67
Nov 28 00:22:19 debian11dhcp avahi-daemon[366]: Joining mDNS multicast group on interface ens18.IPv6 with address fe80::ac3c:d9ff:fe36:a27b.
Nov 28 00:22:19 debian11dhcp avahi-daemon[366]: New relevant interface ens18.IPv6 for mDNS.
Nov 28 00:22:19 debian11dhcp avahi-daemon[366]: Registering new address record for fe80::ac3c:d9ff:fe36:a27b on ens18.*.
Nov 28 00:22:22 debian11dhcp avahi-daemon[366]: Joining mDNS multicast group on interface ens18.IPv4 with address 10.11.12.163.
Nov 28 00:22:22 debian11dhcp connmand[371]: Failed to set hostname to debian11dhcp
Nov 28 00:22:22 debian11dhcp connmand[371]: Failed to set domainname to spidernet.to
Nov 28 00:22:22 debian11dhcp avahi-daemon[366]: New relevant interface ens18.IPv4 for mDNS.
Nov 28 00:22:22 debian11dhcp avahi-daemon[366]: Registering new address record for 10.11.12.163 on ens18.IPv4.
Nov 28 00:22:23 debian11dhcp connmand[371]: ens18 {add} address 10.11.12.163/24 label ens18 family 2
Nov 28 00:22:23 debian11dhcp connmand[371]: ens18 {add} route 10.11.12.0 gw 0.0.0.0 scope 253 <LINK>
Nov 28 00:22:23 debian11dhcp connmand[371]: ens18 {add} route 10.11.12.1 gw 0.0.0.0 scope 253 <LINK>
Nov 28 00:22:23 debian11dhcp connmand[371]: ens18 {add} route 0.0.0.0 gw 10.11.12.1 scope 0 <UNIVERSE>
Nov 28 00:22:23 debian11dhcp connmand[371]: ens18 {add} route 82.165.8.211 gw 10.11.12.1 scope 0 <UNIVERSE>
Nov 28 00:22:24 debian11dhcp dhclient[834]: DHCPREQUEST for 10.11.12.163 on ens18 to 255.255.255.255 port 67
Nov 28 00:22:24 debian11dhcp dhclient[834]: DHCPACK of 10.11.12.163 from 10.11.12.2
Nov 28 00:22:24 debian11dhcp connmand[371]: ens18 {del} route 82.165.8.211 gw 10.11.12.1 scope 0 <UNIVERSE>
Nov 28 00:22:24 debian11dhcp dhclient[834]: bound to 10.11.12.163 -- renewal in 37230 seconds

The same thing happens whether I use virtio or e1000 as my network device.

Has anyone seen this issue?! This is very unusual!
 
Last edited:
Debian 10 - no issue.
Debian 11 - network issue after a network restart
Debian Sid - network issue - network dies within seconds after booting
Ubuntu 21 - no issue.
OpenBSD 7.0 - no issue.
Devuan 4.0 - no issue.

Documenting it here. If anyone has any ideas, do speak up, I'm very curious.
 
ktdt00 said:
Same problem. Debian 11. Appreciate the dhclient workaround - better than rebooting :)
Click to expand...
Glad it's not just me then. I thought I was going crazy for a while. Someone on reddit offered the following suggestion, which seemed to work. Change that "auto lo" line in /etc/network/interfaces to:

auto lo ens18 # replace ens18 with your network device

I'm surprised there isn't more people who encountered this problem, does no one use Debian 11 on promox? :) Or is it just the two of us who encountered this weird problem? Gotta hate that.
 
Isn't auto required if you want ifup to take care of a particular interface automatically? Or is it only at boot? I think the default proxmox install does put it in there.
 
oktay said:
Isn't auto required if you want ifup to take care of a particular interface automatically? Or is it only at boot? I think the default proxmox install does put it in there.
Click to expand...
I'm referring to guest virtual machines.
 
currently my problem. especially if i pulled the Ethernet cable from my switch. but restart of Debian 11 VM init.d/networking does that also for me. im troubleshooting this. but i do do think Proxmox bridge (original post is about Ethernet link) does need to somehow keep its IP address after such cable pull because when Proxmox bridge goes offline, the entire VMs (Debian 11) goes offline and stays offline upon restart of VM’s init.d/networking
 
Last edited:
I'm running 17 Debian Bullseye VMs and 5 LXCs like this and no problems so far with PVE 6.4 to latest 7.1 using supermicro machines and 3 different intel and one mellanox NIC:
Code: 
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug ens18
iface ens18 inet static
        address 192.168.42.76/24
        gateway 192.168.42.1
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 192.168.42.1

# 10Gbit NIC to NAS
allow-hotplug ens19
iface ens19 inet static
        address 192.168.45.16/24
        mtu 9000
 
Last edited:
Dunuin said:
I'm running 17 Debian Bullseye VMs and 5 LXCs like this and no problems so far with PVE 6.4 to latest 7.1 using supermicro machines and 3 different intel and one mellanox NIC:
Click to expand...
Ugh. Why is it doing it for me then? Double Ugh
 
Same thing happened to me running VM Debian 11 and PM 7.3-3

Network was erratic, ping 2 seconds and then wait 10 secs for the next ping. Also no dns resolution.
I have another debian 11 (same config) running perfectly fine.

I had resorted using E1000 but I've just tried the solution above : auto lo ens18 #
and everything is back to normal.
Thank you!
 
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