Hello,

I was wondering if anyone knew the answer to the following question for me:

I have 2 ethernet cards eth0 and eth1. They both have different IP's. I just recently brought the eth0 online, and it is now the default route out of the server. I am now getting warnings from cpanel saying that my dns for the server does not resolve to the correct IP. It is resolving to the eth1 card, and the packets are going out of the eth0 card. This is causing some hosts to reject mail from my mail server (hotmail, etc). So, my question is this:

will there be any repurcussions in changing the DNS entry for my host name to the IP on eth0? This would cause the DNS to resolve correctly, and I think the emails would start getting through to hotmail. I have a number of virtual hosts running on a shared IP (for eth1), but it looks like they do work fine if I put http://ip.for.eth0/~theirusername/ , so I think this should be fine.

One possible problem could be that cpanel checks your hostname for the correct IP, if I change this, it may not work anylonger.

If you guys could let me know of anything that could cause problems by me changing the DNS entry for my hostname, please let me know!

Thanks!

Hi,

Actually you doesn't need to have dns's ip equal to eth's ip at all
The main thing is that yous bind must be visible from Internet. Do not have you route problem right now? Do you ping your dns?

Anyway, there is no problem to change dns ip - only udate time.

What about cpanel - it tests ip, not service, so...

Regards

Ok,

So it should be working fine, yet some of the big free email providers are bouncing the emails. I found this description from yahoo:
http://help.yahoo.com/help/us/mail/spam/spam-18.html

Note where they say:
Maintain accurate reverse-DNS information for your mail servers. Yahoo! Mail makes extensive DNS checks for each connection, and an accurate reverse DNS will ensure prompt processing of your connection and email.

What exactly is this accurate reverse DNS? What I thought they were doing was saying "OK, we recieved this email from this.mailserver, who claims to be 216.xx.xx.5, so lets do a DNS lookup on this.mailserver. Then they do it, and if replies "ip address is 216.xx.xx.5" then they allow it.

If this is the case, then they are recieving from IP 216.xx.xx.5 but when they do a DNS lookup on the host name, they are getting 216.xx.xx.6 back, which would make them not deliver the message.

Now, I could be wrong on the above, so PLEASE tell me if I am (I won't be mad :) ).

Yep

You are right. Reverse is the getting name through ip (from ip)
Some "intellectual" mail servers get back a delivery that doesn't have normal reverse name. As a matter of fact, if you colocate your server - this is a question of your colo company. Becouse They are responsible for your reverse. So, you would ask "Why do not we have reverse name"