How do I setup revers DNS if I am using a nodebalancer

I have set up my DNS to point to my nodebalancer on linode and when I try to change the reverse dns on my server, I get the following error

No match was found for 'www.example.com'. Reverse DNS must have a matching forward entry.

Is there a way to setup reverse dns while using a nodebalancer?

10 Replies

You'll need to start with creating an A/AAAA record in your DNS Manager that points to the public IPv4/IPv6 address of your NodeBalancer.

Once that is complete and the records are updated, you can set the rDNS to point to the NodeBalancer

@jmetz, the doc you linked seems to describe how to set reverse DNS for a Linode's IP. That option doesn't seem to exist for a NodeBalancer, does it?

You're right, @akerl! I got my wires crossed here.

Sorry about that, @penwizard!

There isn't a way to set up the rDNS on the NodeBalancer. You'll only be able to create the rDNS value for your backend Nodes, but not the NodeBalancer itself.

Can you let us know what your use case would be to have the rDNS set on the NodeBalancer?

Thanks for the replies…

I am no expert in DNS and rDNS so I may have my wires crossed. The main reason I need to do this is because we are having issues sending emails and it looks like it is because our DNS/rDNS does not match up.

If we point our DNS to the nodebalancer, I assume any rDNS request will return the rDNS for the nodebalancer and not the server behind it. So how do we get around this without just scrapping the nodebalancer?

Thanks for the additional details.

The main reason I need to do this is because we are having issues sending emails and it looks like it is because our DNS/rDNS does not match up.

This is likely related to the DNS and rDNS records that are set on the backend Linode that is generating the mailing traffic. Your NodeBalancer just balances incoming traffic, so it's not going to be able to actually send emails. Even if you have a Linode that is behind a NodeBalancer, you can still use that for other tasks, as long as the port you are using for your mailing service doesn't overlap with one of the ports you've got dedicated to a service on your NodeBalancer.

If we point our DNS to the nodebalancer, I assume any rDNS request will return the rDNS for the nodebalancer and not the server behind it. So how do we get around this without just scrapping the nodebalancer?

Since you're going to be sending email directly from the backend Linode, you'll want ensure that you have set up your rDNS record and DNS records correctly.

Typically, for a mailing service, you'll want MX, SPF, DKIM, and PTR (rDNS) records created.

I'm having the same problem and the answers on this thread are useless. May as well delete it.

Hi,

I'm trying to set up a mail server on a multi-node kubernetes setup and want to use my node balancer to make the architecture transparent, offer one front-end IP, and avoid having to update lists of IPs in DNS entries every time I change my quantity or configuration of nodes when Kubernetes could be handling this for me in the NodeBalancer config.

@jmetz you asked for a use case, here's one! I don't see why this isn't possible. To make this work, I have to set up a Linode with a rDNS set but have to manage nginx myself.

@ahrotahntee Thanks for sharing your use case with us! We really appreciate this information, and I've included your comment on our internal tracker for this feature request.

Hi @rdaniels,

In case you're keeping track of how many people have similar use cases, I have exactly the same one as @ahrotahntee. Namely, a SMTP server deployed within a Kubernetes cluster. It would be great if one could set the PTR record of the Node Balancer.

For the time being, even though this is not permitted through the user interface, could the Linode staff change the PTR record of a given Node Balancer upon request through a support ticket?

Same problem here about the Email …. but now it seems to affect the X3 certificates for iPhone when issued by Let's Encrypt.

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