[SOLVED] Flapping network interface in KVM-Box for Proxmox 4.2


New Member
Jun 13, 2016

first of all, thank you for providing this great software to the community! During the last year we have made great experiences with two Proxmox-Servers of version 3.4.

i) Now a Proxmox-Version 4.2 has been installed on a fresh hardware at the same hoster
with just a slight change in the network configuration. There are three KVM-Boxes (originally coming from one Proxmox 3.4-Server by backup and restore) and each of these Boxes has three IP-adresses assigned to it (static eth0, eth0:0 and eth0:1).

ii) The Boxes are connected to the sourrounding net via "Briged mode". The boxes seem to work well and are operational and the infrastructure provider has approved the IP-configuration of the boxes.

iii) The KVM - Box has the following settings:

Bridge: vmbr0
Firewall: on
Model: Intel E1000,
see [2] for the output of qm config.

iv) But the boxes are monitored by check_mk via the preconfigured interface-check lnx_if. This check sends packages to the interface from within the KVM-Box and reports in-errors:

CRIT - [eth0] (up) MAC: 62:62:32:65:32:66, 1 Gbit/s, in: 12.03 kB/s, in-errors: 0.19%(!!) = 0.1, out: 845.11 B/s

Performance Data: rta=0.301ms;200.000;500.000;0; pl=0%;40;80;; rtmax=0.488ms;;;; rtmin=0.237ms;;;;
Performance Data: in=12316.117018;;;0;125000000 inucast=195.222016;;;; innucast=0;;;; indisc=0;;;; inerr=0.366239;0.01;0.1;; out=845.113062;;;0;125000000 outucast=1.398367;;;; outnucast=0;;;; outdisc=0;;;; outerr=0;0.01;0.1;; outqlen=0;;;0;

For the output of ethtool, that if used by lnx_if, see [1].

v) According to the in-errors: 0.19%(!!) in-errors: 0.19%(!!) = 0.1 the monitoring server reports critical errors. The interface is reported to be flapping.

vi) This leads to the following questions:

- What are the best steps to pin down this error message to the actual cause? Which files, tools shall be applied?

- Which configuration parameters in proxmox typically influence this?

- Do we have to change something in the monitoring or in proxmox or in both?

The strange point is that check_mk and Proxmox 3.4 do not show such error messages.

Any help is highly appreciated!

With best regards


[1]: Output of ethtool eth0:

ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
Transceiver: internal
Auto-negotiation: on
MDI-X: off (auto)
Cannot get wake-on-lan settings: Operation not permitted
Current message level: 0x00000007 (7)
drv probe link
Link detected: yes

[2]: Output of qm config:

balloon: 4096
bootdisk: ide0
cores: 6
description: ...
ide0: local-lvm:vm-105-disk-1,size=1002G
ide2: none,media=cdrom
memory: 32768
name: real.shk-datacheck.de
net0: bridge=vmbr0,firewall=1,e1000=66:61:36:36:37:37
numa: 0
ostype: l26
smbios1: uuid=e9853546-39d2-4fae-827b-814b6354a996
sockets: 2
Dec 3, 2019
Sorry for the necro post, but it might help others: We changed to vmxnet3 instead of e1000. Hopefully it will stay stable (stable for 4 days now). Sure, not the performance, but enough for our use case: Migration of an old XEN host with nested virtualization to new hardware. The App running in NetBSD is needing a special version of Xen (4.1.4) to run.

virtio is not possible on nested virtualization (nested host does not boot).


Apr 17, 2017
I have the same problem.
Vhost i a Windows 10 LTSC version.
I try VirtIO and vmxnet3. I change the switch, cables, router, PC. and all that i remember
Some solution alternative?


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