Score:0

Server

Debian Server loses network connection

Marco Frost

4/21/24, 5:45 PM

Problem

My debian server seems to lose network connection after a random amount of time (sometime after an hour, sometimes after a week, sometimes something in between). The server is hosted at a datacenter, so I do not have console access, except I order a KVM. When I restart the server remotely and boot in a rescue system, the server regains network connectivity.

At first I was not sure, whether the server froze or the network connection got lost. I ran a script which pinged 1.1.1.1 every minute and logged that to a file. I just checked that file and can now confirm, that the script was still running but could not reach 1.1.1.1 before I restarted the server.

Troubleshooting workflow

Restart server via remote reboot (feature of the datacenter)
Reboot into rescue system (virtual KVM)
Check logs in /var/logs

Question

What can I do to determine the cause of this problem?

0 + 9

networking

debian

debian-buster

A.B

4/21/24, 5:55 PM

Among the myriad of imaginable tests, you could keep running `ip -ts monitor` redirected to a file. Maybe it will give more information about what happens when the connectivity is lost. Anyway, having a remote console available to remotely do interactive actions while the server is still without network connectivity would be way better.

Marco Frost

4/21/24, 6:02 PM

@A.B I'll give ip monitor a shot. Also I will try to get a remote console when the next outage strikes. What would be a good workflow to determine the cause then?

A.B

4/21/24, 6:14 PM

Really, if I knew, I'd have written an answer.

awado

4/21/24, 6:48 PM

Do you get an IP via DHCP or is it a static one? Recently I was experiencing a similar issue with this cause. Also with debian.

Marco Frost

4/21/24, 9:05 PM

@awado It's a static ip.

Gerald Schneider

4/22/24, 5:26 AM

Write a script that gathers all available information about the current network state (IP, link state, routes, iptables etc.) and write it in a file. Call that script via cron. Analyze the file after the next disconnect.

A.B

4/22/24, 10:08 AM

@GeraldSchneider fwiw, that's the role of `ip -ts monitor` all of its own in realtime, except for iptables . (with iptables-nft) `nft monitor ruleset | ts` would also track rule changes in the same way.

A.B

4/22/24, 10:25 AM

`stdbuf -oL xtables-monitor -e | ts` is more useful (displays process name/pid too). There's also `tc monitor` `ethtool --monitor` and probably a few others to complement this.

awado

4/23/24, 9:32 PM

@A.B: Thanks for this hint. BTW: `ts` must be installed manually and is part of `moreutils` in debian.

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EN: Debian Server loses network connection

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