Resolved IP address keeps coming up misconfigured and I have to refix

[Kristian]

I've spotted a problem on my dedicated server running Plesk which appeared to start happening Yesterday (24th Sept 2019) at some point. One of the IP addresses keeps becoming 'unconfigured'.

I have multiple domains running, but one of them, magsdirect.co.uk runs on a dedicated IP (different from the other domains), as I thought it would make sense to do that with the 'main' website which was my first to protect via SSL cert.

It has been running fine for over a year using the Plesk to control it, but suddenly I am seeing the site time-out (I use Cloudflare over the top of it,but I don't think that's the problem).

I investigated - re-started php / apache / ngix / database - but only when I looked in the IP section of Plesk did I find an error: "This IP address is not configured properly. Repair." which the solution can be found here; A website does not work: Connection time out: This IP address is not configured properly

Running the fix sorts the time-out problem - but only for a number of hours - it then breaks again, and requires the same fix. This only started yesterday as I say, and I wonder if a Plesk update has made something unstable?

I'm running: Version 17.8.11 Update #68

 

[scottthepotter]

If you figure out the issue post it, I am having the same problem as of the 25th of September. I'm running the same version. Interesting thing is that it is occuring exactly every 12 hours, have not been able to find a CRON job that runs every 12 hours. See various messages in the logs that show the sympton but can't find any thing yet that is causing the problem.

 

[scottthepotter]

So I have discovered what is happening, but not sure why. At the DHCP lease renewal the IP address is getting dropped temporarily and that causes all virtual IP's to get dropped as well. Bind then stops listening on all IP's. Once the lease renewal gets renegotiated the primary IP comes up instantly but any other virtual IP's do not and that creates the issue, nginx and httpd fail because 1 or more virtual IP's are not available anymore. Any ideas anyone?

 

[ChrisCP]

Have the same problem since a few days. Some domains stop working and IP for these domains is misconfigured. When i click on repair IP, the domains working again a for a few hours. Does nobody have a solution?

 

[scottthepotter]

So I have tracked it down to something that is tied to DHCP lease renewal. It is happening exactly every 43200 seconds which is the time that is shown in /var/lib/dhclient/dhclient--eith0.lease. I know it happens at DHCP lease renewal because /etc/resolv.conf get's modified with 1 second of the incident. It isn't effecting the primary IP that is being renewed, it just effects all virtual IP's and causes them to be 'misconfigured' in Plesk. My issue started at 08:45 MDT on the 27th, I have checked and there were no Plesk autoupdates int he previous 12 hours nor did I have any system updates (DNF or YUM). I did go to previous backups and discovered that /etc/resolv.conf only recently started getting modified on DHCP lease renewal. Don't know if someone with much greater knowledge of networking can help or not. Essentially the only thing that shows up in /var/log/messages is: Sep 28 21:28:29 ws40 named[24741]: no longer listening on 74.208.186.242#53. So BIND loses track of the interfaces quickly after the DHCP lease renewal. I do not believe that this is a BIND problem however.

 

[ChrisCP]

Does anyone have a solution?

 

[Ales]

Perhaps someone else will have the solution within the current parameters, or at least some troubleshooting ideas, but all I can suggest is a different approach: change your networking to static.

Unless there is a valid reason that DHCP must be used, of course...

 

[Anastasios]

Same issue here. It's very annoying having to resync DNS every 12 hours! I will try to change my net to static and let you know the outcome.

 

[scottthepotter]

So I contacted the company I lease my dedicated server from, Ionas (formerly 1and1) and apparently they have a new process for how you deploy additional IP's (Virtual IP's) which requires setting your primary IP as static. I have had a dedicated server with 1and1 in one form or another for over 10 years and this must be recent. I have not made the change yet, but will this evening. But I would suggest you contact your hosting company for guidance. If you are a current Ionas customer you can login and view the link for the process:
Adding a Public IPv4 Address to a Server - IONOS Help.

 

[ChrisCP]

I contacted IONOS Support and they have problems with their DHCP Systems. So our servers working correctly. Don't worry. They are working hard to solve their problems. At the moment we can change to static IP and when the problems are solved back to dhcp.

 

[scottthepotter]

Chris, that's interesting. They did not admit that it was a 'problem with their DHCP servers', even though I specifically asked that question, only that it was happening because I had not followed the process in the article I posted (of course I have never seen that article before now).

 

[ChrisCP]

I will change to static according your IONOS Help article and will report you. When DHCP is working again i will change back

Made the changes and for the time it woks! We will see in 12 hours

 

[Anastasios]

I will change to static according your IONOS Help article and will report you. When DHCP is working again i will change back

Made the changes and for the time it woks! We will see in 12 hours

Chris, the instructions given are for Centos 6 not 7, do you think this is a problem? I've changed the additional IP to static but I don't want to change the primary server IP settings for obvious reasons...

 

[scottthepotter]

Anastasios,
Shouldn't matter at all.

 

[Anastasios]

Anastasios,
Shouldn't matter at all.

Cheers Scot, The additional IP is the one that keeps coming up as misconfigured, so let's see how it goes.

 

[scottthepotter]

Yep, that's because it is a virtual IP running of the ETH0 interface and while ETH0 recovers after DHCP renewal, the virtual IP does not, which eventually brings down nginx, and httpd.

 

[ChrisCP]

I changed main and additional IP to static. Normally at this time the virtual IP get misconfigured but now it works.
Changed according the guide for CentOS 6 also works for me on CentOS 7.

 

[Anastasios]

It seems to be working, I had no issues so far!

 

[ChrisCP]

Yes thats right. Today i recieved a mail that the problems with the DHCP servers are solved.
I think i will remain on static IP. There are no disadvantages.
Just for information, you have to change also the main IP to static not additional IP only.

 

[Anastasios]

Yes thats right. Today i recieved a mail that the problems with the DHCP servers are solved.
I think i will remain on static IP. There are no disadvantages.
Just for information, you have to change also the main IP to static not additional IP only.

Hi Chris, yes that's right, initially I changed only the additional one and had the same problem. Now both primary and secondary IPs are set as static and I have no issues at all. I will also remain on static IP just to be on the safe side