During an Incident I was dealing with an issue that an amount of different *nix machines were receiving / transmitting data over the wrong interface.
Since we didn’t want to check every *nix machine manually to see which interface is used I wrote a simple bash script which collects necessary network interface statistics like received / transmitted bytes for every interface configured over time.
The script writes a log to a separate file with following format:
Wed Jan 21 14:58:13 CET 2015 NIC=eth7 RXbs=2807182787 TXbs=192412352
while NIC = Interface, RXbs = Received bytes per second and TXbs = Transmitted bytes per second.
We executed the script every minute by using the crontab and we collected and analyzed the log by using Splunk.