Sap IT notes

Virtual machine packets loss.


There are such thigs you want to write down to rememer and while you’re noting it helps you to remember it better. Here is the one of them.

VM running on KVM hypervizor in OpenStack platform gets under packet loss issue – 20% ICMP packets loss.

On hypervisor dmesg shows:
...
[Thu Jul 14 01:51:46 2016] nf_conntrack: table full, dropping packet
[Thu Jul 14 01:51:46 2016] nf_conntrack: table full, dropping packet
[Thu Jul 14 01:51:46 2016] nf_conntrack: table full, dropping packet
...

It straight tells us about full tables nf_conntrack – iptables component which tracks connections states.
A command sysctl -a | grep nf_conntrack_max shows us default value for records count:

[root@fedora23 ~]# sysctl -a | grep nf_conntrack_max
net.netfilter.nf_conntrack_max = 65536
net.nf_conntrack_max = 65536

Let’s increase it. In file /etc/sysctl.conf append: net.netfilter.nf_conntrack_max=524288 and apply new settings: sysctl -p.
That’s it, the issue is solved and now packets don’t be droped.

Leave a Reply

Your email address will not be published. Required fields are marked *

© 2015