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Reverse DNS lookup

 
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Super Advisor

Reverse DNS lookup

hi

What kind of problems could have a name server (DNS server)
or a webserver if his Reverse DNS lookup doesn't work.

kind regards
chris


10 REPLIES 10
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Honored Contributor

Re: Reverse DNS lookup

does the server has reverse lookup zone?
if so:
attach /etc/named.conf and the file of reverse lookup zone
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Honored Contributor

Re: Reverse DNS lookup


simple:

all network establishing request to that server will be delayed by minutes.

the server will try to reverse lookup the connection query to find out the server name, if it is not able to find out depending on the security of the application it either discards the connection or times out and accepts it

Regards,
Gopi

Never Never Never Giveup
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Honored Contributor

Re: Reverse DNS lookup

the nslookup utility and such won't work.
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Exalted Contributor

Re: Reverse DNS lookup

It usually is the format of the reverse lookup records. I'm going to attach a proper example for you.

It could be the reverse zone is not listed in /etc/named.conf

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
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Trusted Contributor

Re: Reverse DNS lookup

Hi,

Any network application using tcp wrapper (such as telnet) will experience a delay while trying to establish a connection.

Apart from that, when you do nslookup, your DNS server's name would be 'unknown' since the IP od DNS server will not have a PTR record.

Regards
What we cannot speak about we must pass over in silence.
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Honored Contributor

Re: Reverse DNS lookup

There will be some applications that will not work, or will not work well. Some applications have a higher dependence on lookups by name as opposed to IP address.
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Respected Contributor

Re: Reverse DNS lookup

can u be more clear...
u mean , ur server's ip doesnt have a reverse dns entry OR ur server cannot do any other ips reverse dns lookup ?
Be Always Joy ......
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Super Advisor

Re: Reverse DNS lookup

It's not my server,
I mean every server without reverse DNS lookup,
for example:

bsd# host 212.244.86.18
Host not found.

I think some mail servers will deny the mails from the servers without reverse DNS lookup.

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Exalted Contributor
Solution

Re: Reverse DNS lookup

To deliver mail to aol and me, you must have reverse lookup records.

You don't need them for every server. You need them for the ip address that is actually being used to send the mail.

If the mail from server1 is relayed by relay1, the IP address on the public Internet that does the actualy work of transferring the mail to other servers needs a reverse lookup address for that IP address.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com