Assigning IPv6 IP to server IP (while maintaining IPv4 server IP)

[TomJones]

I recently started failing SPF checks with Gmail and Comcast emails, finally figured out it was because Exim was communicating with those servers using IPv6. I didn't have any IPv6 IP assigned to the server, Exim was using an IP from who knows what/where, so I went in and turned off IPv6 support in /etc/exim.variables.conf. Immediately all good again sending emails, but decided I needed to get with IPv6 now, so I reached out to my dedicated server provider and they gave me a block of IPv6 addresses to use.

Here's where I am stuck. In my mind, I should add a dedicated IPv6 address and assign the server as the owner of the IP (while the server also responds on the dedicated IPv4 address it's been on). I added the IP via IP Management, and it's now listed in there as "free" but I can only assign it to "admin" via the tool. It's been awhile since I messed with any of this, and I realize I might be trying to do something the wrong way, so I came here hoping someone can shed some light on what I want to do. I should be adding the IPv6 to the server while keeping the IPv4 address for it, correct? If so, what is the process for doing that exactly? I'm just nervous about screwing something up, and then my server stops responding on the dedicated IP and I'm in a real mess.

Thanks in advance for any feedback!

 

[TomJones]

Updating my bumblings on trying to accomplish this myself. I added an IPv6 address from the range my provider gave me via IP Management on Saturday. I then linked the v6 address to the server IP, which created a set of AAAA records in the DNS settings for the server. Everything seemed to go okay, but in all the testing I did, I couldn't get the server to respond on the v6 address. I gave up after a few hours of trying to get it working. I didn't have a chance to work on it the next day (Sunday), though I did casually notice I hadn't received a single email all day, but it was Sunday, maybe the spammers had found religion, I thought. Of course, later that night I get a call from one of the clients on the server, they haven't gotten any mail all day and they can't send any. Oh boy....

Not knowing what could be the cause, the first thing I did was go in and unlink the v6 IP from the server IP (the only real change I had made on the server). Still no mail in either direction, so I restart the server and start checking the DNS records. I go into the backups I keep for each site and start looking for where the DNS record backups are kept. I was sure they had to be in a file somewhere, but I searched and searched without any luck. I was just about to give up with I opened the file /backup/<sitename>/<sitename>.db and found the old DNS settings (which coincided with my recalling zone files have db extensions). Sure enough, something I had done (I'm thinking it was unlinking the v6 IP) caused the "smtp" and "mail" A records to be stripped from all sites that were using the server IP to send mail. Once I added those A records back to each site, mail resumed.

I've decided to put this one on a backburner for awhile. My server doesn't really need to be communicating via IPv6 at this point (does it??).