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items: I need to refresh ARP frequently.

I need to refresh ARP frequently.
type: item
description: I've been using OpenVZ for several years both personally and at work. It's been a big part of my daily life but I have not kept up with changes over the years; it's been so robust that I just depend on it working. Recently, however, it all fell apart. I use tinc at work to make a campus network available to my OpenVZ servers at Amazon (AWS). This has worked for a year or so with occasional network drops to individual VEs. I usually just restart them and they work again for quite awhile. Last weekend there was a network hardware upgrade on campus. There were lots of disruptions and suddenly my VE connectivity was up and down constantly. It was a nightmare. Restarting VEs helped but only momentarily; there were always several VEs offline. I dug into the startup sequence to see what it was that seemed to fix (for a moment) the situation. The key was periodically sending ARP updates to my neighbors on the tinc interface using arpsend. I have attached the Python script I kludged together to do this once a minute. This script seems to solve the problem for me. I hope that it helps someone else. But I would also be delighted to hear that all I needed to do was set some sysctl value so that my neighbors don't lose my ARP entries. I suspect it's a bit more complicated, though. (I am using 2.6.32-openvz-042stab112.15-amd64.) Thank you for OpenVZ! --kyler
creator: kylerlaird
date: 2016-07-14T13:36:31-00:00