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MX Record Shows Private IP Address

Posted on 2011-05-06
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Last Modified: 2012-06-27
I have a customer with a DSL connection from Bell Canada. I'm using the static IP address to point to a new exchange server.

Now when I do a mx record check http://www.mxtoolbox.com it comes back as the record but for IP I show 0.0.0.0

When I click on the IP it says 0.0.0.0 is a private IP address. Private IP addresses cannot be reversed publicly.

Why is that?
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Question by:Gerhardpet
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Expert Comment

by:zazagor
ID: 35704678
Hi,

Private addresses can be used on multipal sites on internet but only in private networks therefore
they can not be routed or reversed publicly.

//zazagor
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Expert Comment

by:Netflo
ID: 35704808
Hi Gerhardpet,

I would suggest looking at your DNS records, either via your domain registrar or hosting provider who ever handles your DNS and ensure that the MX record points to a valid A record which maps to a static IP.

It appears that a mistake has been made by someone, hence MX Toolbox is simply reporting records that have been incorrectly set.

You should not configure MX records to go to IP addresses directly. For example your end setup should be:

MX: mail.domain.com -> A: mail.domain.com -> IP: 1.2.3.4
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Author Comment

by:Gerhardpet
ID: 35705287
Netflo,
that is what I have setup in DNS. Take a look your self

The domain is featurefoods.ca
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Author Comment

by:Gerhardpet
ID: 35705299
and it is not a privite IP. It is a public static IP from Bell Canada.

I have used Bell with static IP's before with no problems
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Accepted Solution

by:
Netflo earned 2000 total points
ID: 35705336
You're right, everything looks okay via nslookup and Who.is

Take a look for yourself: http://who.is/dns/featurefoods.ca

There appears to be incorrect information being displayed on MX Toolbox. Take a look on http://lookupserver.com/ and put in remote.featurefoods.ca under DNS Lookup, results are correct.
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Author Comment

by:Gerhardpet
ID: 35705337
Depending where you are in the world you may not see the new mx records becuase I just change the DNS 12 hours ago.

Here is an attachment
 mx
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Expert Comment

by:Netflo
ID: 35705355
I'm in the UK and I saw the same results. I performed a NSLOOKUP via Google DNS servers and its reporting the correct information, along with the other sites I listed above.

MX Toolbox is not fully up to date.
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Expert Comment

by:Chris Dent
ID: 35705386
The TTL for those records is very short and it should have figured it out by now. Anyway MXToolbox is wrong, that's not your MX record set.

Chris
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Expert Comment

by:Netflo
ID: 35706117
Chris, I believe TTL values values would kick in if the record was already present. If the record was newly created, the initial DNS propagation times would apply.
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Author Closing Comment

by:Gerhardpet
ID: 35706177
Thank you for your help on this Netflo
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Expert Comment

by:Chris Dent
ID: 35706195
> the initial DNS propagation times would apply

There's no such thing as initial propagation times. It suggests that "everywhere" maintains a persistent copy of the zone (positive and negative), which isn't true. Negative caching is typically no longer than 5 minutes, positive caching is dictated by the TTL. The oft quoted 24-48 hour thing is a myth.

Chris
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Author Comment

by:Gerhardpet
ID: 35706212
Interesting. I don't know much about DNS caching but I had a case a while ago it took 68 hours or so for the cashing to complete
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Expert Comment

by:Chris Dent
ID: 35706249
You normally see delays when:

 - The Host or Provider fails to perform an update you've requested (these will be the people hosting your DNS domain, not third-parties)
 - Multiple changes, where NS records are being changed in addition to other records and all have long TTLs

In the few, very, very rare cases:

 - Where an organisation has enforced a Minimum TTL (exceptionally rare, and something few DNS platforms permit)

AOL used to be guilty of the last, especially evident in their mail platform, but we haven't really seen them do that since 2005.

That's it really, everything else is driven by the TTL, and even that doesn't apply for brand new records.

Chris
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Author Comment

by:Gerhardpet
ID: 35706271
In the case were it took 68 hours or so I was changing the DNS from another provider (can't remember the name) to Go Daddy
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Expert Comment

by:Chris Dent
ID: 35706294
It's likely the NS record TTL was high, probably on your DNS hosts end. But it's equally possible that the change on the TLD* holder took a long time to process (an administrative failing, not a limitation of DNS), you see a hell of a lot of variation there, anything from a couple of hours, to a few days.

*TLD is Top Level Domain, like .com, .net, .co.uk, etc

Chris
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