While SSHing into my server with an RSA key, I get this message:
Address 255.100.236.105 1 maps to a1.example.com, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Even though I get this error, I am still able to SSH into the machine.
I examined the DNS and figured out the issue. This server has lots of vhosts, so we have multiple A records for the same IP address.
For example:
A a1.example.com 255.100.236.105
A ssh.example.com 255.100.236.105
(there are a few more that point to the same IP)
I am trying to SSH to ssh.example.com
, and I am getting the above error. How do I get SSH to realize that the IP has multiple domain names that point to it?
NOTE: I can't ssh to a1.example.com
because that subdomain is going through CloudFlare's proxy.
UPDATE: I tested this on two computers. One gave me that error, one did not. Why would that be?
1 This is a fake IP, I made up. I'm not sure if it really points anywhere.
If you put the reverse DNS name for
ssh.example.com
in your hosts file, that will usually be the first response returned by DNS.