Questions tagged [reverse-dns]
Reverse DNS lookup is the determination of a domain name that is associated with a given IP address using the Domain Name System (DNS) of the Internet.
562
questions
307
votes
14
answers
992k
views
What's the command-line utility in Windows to do a reverse DNS look-up?
Is there a built-in command line tool that will do reverse DNS look-ups in Windows? I.e., something like <toolname> w.x.y.z => mycomputername
I've tried:
nslookup: seems to be forward look-...
- 3,205
121
votes
15
answers
148k
views
What's the reverse DNS command line utility?
What's the command to find the name of a computer given its IP address?
I always forget what this command is, but I know it exists in Windows and I assume it exists on the *nix command-line.
- 2,208
35
votes
6
answers
60k
views
Multiple Reverse DNS Entries?
I'm a DNS noob, so here's a question:
Can a server have multiple reverse DNS entries? Or does one IP address just resolve to one DNS name?
Here is why I need this:
I have a number of sites hosted ...
- 896
27
votes
1
answer
5k
views
Do internet standards require reverse DNS for every device?
The requirements surrounding reverse DNS are confusing! People frequently talk about everything breaking if reverse DNS is not present, and that sounds scary. Even in cases where applications don't ...
- 32.8k
26
votes
3
answers
4k
views
Has my ISP mangled my DNS reverse lookup record for a single static IP address?
I've taken on the task of running a small email server, and the world of spam makes it more challenging for an individual, as many MTAs are highly paranoid about accepting email.
I think I've ...
- 271
25
votes
4
answers
22k
views
Reverse DNS in a CIDR world
Reverse DNS seems to be strongly tied to class boundaries, what methods exist now that CIDR is the standard to delegate authority for a subnet? If multiple methods exist which one is best? Do you ...
- 131k
22
votes
1
answer
6k
views
How can this tool find out registered domains from an IP address?
This is one that I've never really known how to do, and it's been nagging me from time to time for years. I've read all I could find, including all the answers here. None of them gives a real answer ...
- 333
21
votes
5
answers
3k
views
Is it good practice or too draconian to reject mails from mailservers with no RDNS
I've recently dropped SpamAssassin and am now basing spam rejection on DNSRBL's, grey-listing and other basic tests and I'm wondering whether I should also block hosts that don't have a valid RDNS ...
- 586
21
votes
3
answers
24k
views
Will adding a second SPF record mess up my DNS?
Will adding a second SPF record mess up my DNS, or will it be like adding an extra nameserver?
(i.e. it only helps, not hurts)
- 1,045
19
votes
2
answers
27k
views
PTR record (rDNS) for multiple domains on a shared IP address
I host multiple domains on a single IP address:
cats.com
A @ --> 10.20.30.40
A mail --> 10.20.30.40
MX @ --> mail
dogs.com
A @ --> 10.20.30.40
A mail --> 10.20.30.40
MX @ --> ...
- 417
17
votes
5
answers
196k
views
Reverse DNS - how to correctly configure for SMTP delivery
I started a new service and we need to send emails to our customers (new account confirms, etc).
My server is known as prod01.bidrodeo.com and resolves to 97.107.134.38 .
For reverse DNS, 97.107....
14
votes
1
answer
4k
views
Is it OK to use my public domain name as my internal AD domain name instead of using .local internally?
I am taking over a project and the local domain name is domain.com; they also have a website at domain.com.
I have always used domain.local for AD, and am wondering if that is a best practice or is ...
- 9,566
13
votes
2
answers
4k
views
Detect spammers on my server
I recently got one Undelivered Mail Returned to Sender while sending my newsletter to one of my 1500 customers. My website uses a double-opt-in procedure to make sure, the user explicitly want to ...
- 271
13
votes
1
answer
2k
views
How to force an ISP to remove false reverse DNS?
There is an IPv4 address (in a /8 managed by ARIN) that I have no control over which reverse resolves to a domain name which I registered. Someone used the IP address to run a scam, and it is ...
- 413
12
votes
3
answers
3k
views
What is reverse DNS?
I've lot of *.in-addr.arpa domains requests in my OpenDNS account. I know this should be normal and it's about reverse DNS.
I've been reading here and there but still I can't really get how it works ...
- 2,019
11
votes
4
answers
86k
views
How to setup PTR (Reverse DNS) at Godaddy DNS manager
My hosting provider already did PTR setup. Now i have to setup it at my DNS holder i guess. What am i supposed to do at my Godaddy account. thank you.
my ip : 64.250.113.235
and you can check my ptr ...
- 556
11
votes
5
answers
10k
views
Apache httpd won't stop doing reverse DNS requests for clients' IPs
Obviously my Apache httpd instance is doing reverse DNS (RDNS, give me the hostname for this IP address) lookups for each incoming client connection's IP address. This is bad. Especially since ...
- 1,978
11
votes
2
answers
44k
views
Reverse DNS is not a valid hostname [closed]
I help a friend run a server, which includes a mail server. http://mxtoolbox.com reports that our reverse DNS is not a valid hostname.
The reverse DNS currently points to domain.com. Should it point ...
- 939
10
votes
4
answers
34k
views
Reverse DNS Setup for an IP with multiple domains
I am trying to clarify my Reverse DNS PTR lookup for a domain. I have a server with a single IP addresses and multiple accounts, all sharing that IP address;
My PTR is currently:
24.210.31.in-addr....
- 219
10
votes
3
answers
19k
views
Is it bad to have the reverse DNS for two IPs point to the same domain name?
I am in the process of setting up a new server for my web application (the site will be moved, it is not for load balancing or the like), which has a different IP address from my existing server. My ...
10
votes
1
answer
10k
views
Remote connection to MySQL server takes very long
I have a MySQL 5.0.75 server running on my Linux notebook to which I want to connect from another machine in the local network.
This connection takes 5-6 seconds:
mysql -h 172.22.65.101 -u myuser -...
- 203
9
votes
5
answers
10k
views
How important are PTR records for Email Servers?
Does anyone know of any studies done to show how much email will be rejected if there is not ptr record for the SMTP banner name of an email server?
Are reverse checks always done when enabled, or ...
- 84k
9
votes
4
answers
20k
views
How does a Reverse DNS lookup work with regards to spam filters?
I have heard that most spam filters use a reverse DNS lookup on the originating IP address of the sending SMTP server (or something like that) as part of the verification process. I want to make sure ...
- 193
8
votes
6
answers
26k
views
sshd tries reverse DNS lookups with UseDNS no
sshd seems to almost always try to perform a reverse DNS lookup on new connections. For hosts without a PTR entry this causes delays of 5 seconds per query. Sometimes it accepts the connection ...
- 191
8
votes
2
answers
5k
views
How do I perform a LLMNR query?
I wish to perform a LLMNR query explicitly. My current environment includes DNS servers so the ping (ping -a specifically) is doing DNS queries to resolve the name. I can disable my DNS in my ...
- 1,046
8
votes
3
answers
15k
views
Disable reverse lookup in rsync daemon
I'm having an issue with some rsync modules being served through rsync --daemon
This lines are from my /var/log/rsyncd.log file :
2013/02/08 12:15:28 [13174] name lookup failed for XXX.XXX.XXX.XXX: ...
- 302
7
votes
6
answers
13k
views
How do I change reverse DNS on Google Cloud Compute?
How do I change reverse DNS on Google Cloud Compute?
I want to add reverse DNS to Google Cloud Compute and can't figure out howto do it.
I want to map 11.97.196.104.bc.googleusercontent.com to ns1....
google-compute-engine
7
votes
6
answers
10k
views
Finding all domain names that resolve to the same ip?
Lately I've been tracking a spammer on craigslist. I recently discovered that he's added a new technique to his arsenal, he registered a whole bunch of domain names but they all resolve to the same ip ...
- 264
7
votes
2
answers
660
views
Is it valid to have several IP addresses resolving back (PTR) to one name that doesn't match either of the relevant A records?
I have several devices, each with its own IP address. There are various names pointing to these addresses (in several different domains). As an example the device with
IP address 10.0.0.1 is known as ...
- 3,617
7
votes
2
answers
6k
views
How to determine which DNS server has the authority to set rDNS (PTR records)?
or to re-phrase... How to determine to whom authority has been delegated to set rDNS?
Background
In a multi-tier environment, where a block of IP's is assigned, then further split and assigned (...
- 586
7
votes
2
answers
3k
views
How are DNS PTR records managed?
As I understand it, an IP address-owner can set up a DNS PTR record for his IP address to map the IP addresses to its host names. There are some things about this I don’t understand. I’ve managed ...
- 71
7
votes
1
answer
12k
views
Reverse DNS is not a valid Hostname error from MXToolBox
I can't send email messages from my server. However, I can receive email messages. I set up my server the exact same way I did many times which I've proven it works and it's pretty straightforward and ...
- 171
7
votes
3
answers
21k
views
how to add a REverse PTR Record on Amazon Route 53?
if i have the below ip 168.144.254.X and i would like to add a ptr record in amazon in the form of
X.254.144.168.in-addr.arpa what should be in the name field and what should be in the
value field
...
- 193
7
votes
2
answers
12k
views
sshd warning, "POSSIBLE BREAK-IN ATTEMPT!" for failed reverse DNS
Whenever I SSH somewhere I get something like this in the logs:
sshd[16734]: reverse mapping checking getaddrinfo for
1.2.3.4.crummyisp.net [1.2.3.4] failed - POSSIBLE BREAK-IN ATTEMPT!
And it ...
- 173
7
votes
1
answer
431
views
Best Practice: notify email sender that their reverse lookup is broken
This probably should be a wiki, not entirely sure. Before I begin, the external server that performs scanning is a custom amavis/postfix/fortigate pipeline; it is suggested that any changes work ...
- 14.6k
6
votes
3
answers
4k
views
Ping hostname returns another hostname in output : what does it mean?
When I ping the server sip3.voip-centrex.net, I get this output:
PING sip3.voip-centrex.net (194.98.81.144) 56(84) bytes of data.
64 bytes from mpfrrelay.michaelpage.fr (194.98.81.144): icmp_req=1 ...
- 453
6
votes
3
answers
16k
views
How to configure bind9 to be a local DNS only with no internet access?
I want to configure bind9 to be a local DNS only with no internet access at all. So I have 5 PCs in my virtual domain xy.com. Within this domain there is no access to the internet.
The DNS server ...
- 1,259
6
votes
3
answers
9k
views
SMTP host name vs. domain in "From:" address vis-a-vis Email Deliverability
I'm trying to implement (or make sure that I'm correctly following) email sending best practices to improve deliverability, but the role of the smtp server's host name vs the domain name of the From: ...
- 61
6
votes
6
answers
717
views
Should every IP address be reverse and forward resolvable?
Will there be trouble if non-server machines:
1. don't have forward addresses that match in-addr.arpa?
2. don't have forward addresses?
3. don't have in-addr.arpa PTRs?
- 13k
6
votes
1
answer
8k
views
Disable DNS Caching PHP
I need to get the latest A records of a DNS in a script. The script is doing some monitoring operations. The Default TTL of DNS record is 5 minutes, but the monitoring script is running every minute. ...
- 1,147
6
votes
4
answers
7k
views
SSH reverse DNS lookup
I was wondering why I'm connection to a server with SSH, it does a reverse DNS lookup on the IP of the remote server.
I have found comments telling that it was for security reason, lots of tutorial ...
- 163
6
votes
1
answer
3k
views
Reverse DNS Lookup for 10.* Failing
I am trying to configure NSD and Unbound to handle Internal DNS.
I have everything working for forward look ups but reverse looks ups are failing.
I am not sure what to do next, but looking at the ...
- 61
5
votes
3
answers
1k
views
With regard to anti-spam practices, what exactly does a typical reverse DNS check look for?
My understanding is that a typical reverse DNS lookup will compare the SMTP hostname (provided in the EHLO/HELO command) of an incoming connection and verify that it matches the PTR record for the ...
- 11.9k
5
votes
2
answers
20k
views
Is it possible to set up a reverse DNS record on AWS for address from a different registrar?
I don't have control over the registrar for the domain we use but the elastic ip and domain have been registered to each other - now I need to set up a mail server on my EC2 instance and therefore be ...
- 169
5
votes
3
answers
17k
views
How do you configure BIND to forward reverse DNS queries to another DNS server?
I've got 2 domains in my environment. One of them is an active directory domain for 'myproductionlab.local' at 10.60.0.0/16
Then I have a debian box running bind9 for a domain, 'mytestlab.local'
I ...
- 405
5
votes
1
answer
11k
views
MXToolbox: "Reverse DNS is not a valid Hostname"
I know that there is another thread about this topic here on serverfault.com but it did not solve my issue.
I have also googled it and it seems that SPF record could be mis-configured in some cases ...
- 261
5
votes
2
answers
16k
views
Do I need to Set-up PTR record in SPF Setting?
I have set-up the RDNS from my hosting provider for the ip address to resolve to "maximus.example.com". After that, do I also need to add the PTR records to the SPF Text details in my DNS zone file as ...
- 1,451
5
votes
2
answers
6k
views
Are PTR records added only by the ISPs that provide and manage the IPs?
I am administering a network with many locations and work with multiple providers I checked out with my DNS provider to change the PTR records for one of the IPs, they replied:
Dear Sir,
We ...
5
votes
2
answers
1k
views
How to confirm who is responsible for serving reverse DNS (PTR) requests an IP block?
Before anyone answers "ask your ISP" or "ask your hosting provider", please read in full.
Scenario:
I own a domain name mydomain.example, and a publically routed IP block (say 192....
- 327
5
votes
1
answer
24k
views
Reverse DNS does not contain the hostname error from MXToolBox
I am not sure where I have gone wrong in my configuration but I am getting the error Reverse DNS does not contain the hostname for my domain sparkdojo.com I had the hosting company set the PTR record ...
- 53