Intermittent Network disconnection, Ubuntu, troubleshooting

Question

I purged network manager from my system (OS: Linux 3.13.0-53-generic #89-Ubuntu)

Networking service runs on my system:

sudo service networking status
networking start/running

Static interface info:

iface eth0 inet static
address 100.100.100.216
netmask 255.255.255.0
broadcast 100.100.100.255
gateway 100.100.100.1
dns-nameservers 123.132.134.35
dns-search google.com

Problem: Internet connection disconnects randomly.

Troubleshoot:

I have another windows machine on my LAN that works, when network is not connected on Linux. So, no problem with router

Try to ping gateway

ping 100.100.100.1
PING 100.100.100.1 (100.100.100.1) 56(84) bytes of data.
From 100.100.100.112 icmp_seq=1 Destination Host Unreachable

So, to test this random behaviour I assumed the network traffic might be causing the random behaviour.

So, I did set one of the shell to infinitely ping Google server. After a while as expected I got the following message

ping: sendmsg: No buffer space available

After some time, the network starts working again.

On one of the link it says to increase the size of the buffer (www.cyberciti.biz/faq/linux-tcp-tuning). So I did, and my current proc/sys/net/core/wmem_max size is 83886080

Still, if I do infinite ping again network fails the same way.

Question: Which process/service is causing the network buffer reset? Also, why is it taking so much time to do so?

As a temporary fix, manually unplug-plug Ethernet or do ifdown eth0 && ifup eth0 [But, this is not a correct solution]

Answer 1

I wrote about this just yesterday. Sigh.

The root cause is probably that there is another computer on the network that has the same IP address. Sometimes this is caused by assigning an IP in the a range that DHCP thinks it has control over.

To verify there are conflicting IPs when you Linux box loses network connection, get onto your windows box and see if you can ping 100.100.100.216.

The "buffer space" condition was mentioned by Claris.