Contents

Reverse DNS

Brightbox Cloud IPs have a default generic reverse DNS entry. For example:

$ host 109.107.38.125
125.38.107.109.in-addr.arpa domain name pointer cip-109-107-38-125.gb1.brightbox.com.

And the forward DNS entry works too, as you’d expect:

$ host cip-109-107-38-125.gb1.brightbox.com
cip-109-107-38-125.gb1.brightbox.com has address 109.107.38.125

You can customise the reverse DNS very easily using the cli (since version 0.14). Firstly you need to set up your normal forward mapping using your usual DNS provider. In this case I’m setting up reverse DNS for my mail server, so I’ll use mailserver.example.com. So I’ll confirm that is working correctly:

$ host mailserver.example.com
mailserver.example.com has address 109.107.38.125

Note: It’s important that you set up the forward mapping first, Brightbox Cloud will reject attempts to set up a reverse DNS entry if your corresponding forward DNS entry is missing.

Showing the help for the brightbox cloudips command reveals some DNS options:

$ brightbox cloudips help update
update [command options] cloudip-id
    update Cloud IPs

Command Options:
    --delete-reverse-dns  - Delete the reverse dns for this cloud ip
    -r, --reverse-dns=arg - Set reverse DNS for this cloud ip

So now I need to find the identifier of this Cloud IP:

$ brightbox cloudips list | grep 109.107.38.125
 id         status    public_ip       destination  reverse_dns                         
----------------------------------------------------------------------------------------
 cip-wh8d7  unmapped  109.107.38.125               cip-109-107-38-125.gb1.brightbox.com

My identifier is cip-wh8d7. I can now update the reverse DNS:

$ brightbox cloudips update --reverse-dns=mailserver.example.com cip-wh8d7                
        
 id         status    public_ip       destination  reverse_dns     
--------------------------------------------------------------------------
 cip-wh8d7  unmapped  109.107.38.125               mailserver.example.com
--------------------------------------------------------------------------

And the DNS should be configured instantly:

$ host 109.107.38.125 
125.38.107.109.in-addr.arpa domain name pointer mailserver.example.com.

Invalid reverse DNS

If the forward DNS mapping is later removed, or changed to point at a different address, the reverse DNS mapping will eventually automatically switch back to the default. See the reverse DNS reference docs for more information.

Removing custom reverse DNS

It’s simple to manually remove the custom DNS and go back to the default:

$ brightbox cloudips update --delete-reverse-dns cip-wh8d7

 id         status    public_ip       destination  reverse_dns                         
----------------------------------------------------------------------------------------
 cip-wh8d7  unmapped  109.107.38.125               cip-109-107-38-125.gb1.brightbox.com
----------------------------------------------------------------------------------------

Last updated: 25 Apr 2016 at 09:24 UTC

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