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The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.

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I have 300 Ubuntu 14 PC's that I block all internet except a whitelist - I do this by disabling dns, and have the central server do dns lookups for everything on whitelist and put it in a hosts file and have all the hosts use that. Obviously, this is a bit hacky but it worked.

The problem now - I have a need to whitelist *.slack.com. Slack says subdomains change too much, they cant provide a static list, or even a current list and then let me update it.

So I guess I need to enable DNS - what might be easy ways to still restrict to a whitelist of domains? I can easily run shell scripts on all 300 machines. (they check in with central server and grab a script and run it regularly). So anything I can install/configure via script is a viable option...

If it's not too hard I could set up an ubuntu machine to be a dns server.

Basically what I want is whatever is easiest so that I can just provide a whiltelist, that is allowed to have wild cards like *.slack.com and block everything else. I suppose it doesn't actually have to be a DNS based block if there is some client app.

Whatever it is, I am OK to set up a server myself - but the clients, it needs to be scriptable install/config.

I want to be able to update the whitelist easily/quickly.

Any ideas/suggestions?
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I have a whitelist like this...

*.slack.com, *.slack-msgs.com, *.slack-files.com, *.slack-imgs.com, *.slack-edge.com, *.slack-core.com, *.slack-redir.net

The way I have my web filter set up I can't whitelist by stars.... Is there a way I can perform a dns request that would find out what all subdomains are currently defined for *.slack-files.com?  If I can do that I could write something that would do that every 5 minutes and update my hardcoded white list.  

is this possible?  thanks!
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I'm trying to add a server (Server B) as a child domain to an existing forest.  The server was originally setup as a domain controller to replace the on prem domain controller, but was later decided to make is a child of the forest since the NAS on site can communicate with multiple domains of the same forest. I have removed the ADDS role and demoted the server. The old domain controller has a functional level of Windows Server 2012 R2 and the domain is called XYZ.com. This server was originally setup on a 192.168.60.0/24 network. IT Management has setup the new server (Server B) on a 10.10.16.0/22 network and want to make it a child so that it's domain would be abc.xyz.com. Management has also added a 10.10.16.x IP address on XYZ. On XYZ, I have setup a new site in AD Sites and Services with the 10 subnet and have renamed the original Site for clarity and have set it up with it's 192 subnet. Both servers are manually configured with IP/Subnet Mask/Default Gateway/DNS. Both servers have 2 IPs, one on the 10 network and one on the 192 network. From Server B, I can ping xyz.com by IP but not by name. When I try by name, the replys come from the hosted website. Each network has it's own default gateway. I then go to server B and add the AD DS role and then proceed to Promote the server. I choose the option to "Add a new domain to an existing forest". The "Select domain type" is set to Child Domain. I click on the Select button next to parent domain name where it asks me for …
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Hello
i have installed windows server 2008 R2 with two network adapter each o adapter has different ip address
i have 4 domain on this server
3 domain has pint to second adapter ip address but on of them has point to first adapter ip address
i did the dns forward records changing, reset ipconfig with flushdns and regenerate the dns with /registerdns
but the domain has point to old address yet
i also removed that domain from dns server and added it again, but the problem is still there
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We have a domain controller running Windows 2012 Server and it's also our DNS/DHCP server.  Non Windows devices acquire a DHCP lease, but fail to register in DNS.  Yesterday I added a non Windows device to the network, which immediately showed up in DHCP, but not in DNS.  This morning it finally did show up in DNS.  I added another device today and change the scavenge setting to 1 hour, but it still does not register with DNS.  I do have it checked to dynamically update DNS.

Maybe it tomorrow it will magically show up in DNS, but shouldn't it immediately be added to DNS when a DHCP lease is created?  How can I get this to happen without manually add it?
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When my site are in development I have always gotten the IP address from AWS, then accessed them from my browser. But here's an article I would read if there is a secret exposure...

https://www.imore.com/how-edit-your-macs-hosts-file-and-why-you-would-want

I do not take lightly to changing my Hosts file because I do not want to put myself into an unstable condition, if I missed something in the directions.

Is there risk to using an IP address to directly access my PC? I assume the biggest benefit is that the site can be kept private from public view, but is there any way in the world that someone cold guess that address?

Are the scrapers out there pinging billions of IP addresses?

As far as keeping it private, it is mainly that I can use my real domain name and keep that private? That's nt important to me since I can buy the SSL cert and do that before launch. AT the moment, I just need to look at the sire and test it, so by adding my IP into the browser, does that expose my IP to scrapers?

Thanks.
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I know this is okay but I wanted to see if anyone could explain to me why our conditional forwarders do not resolve the "Server FQDN". I attached a screen shot. The conditional forwarders are on a domain that is setup on a trust relationship.

Everything else resolves and validates.
DNS-forwarders.bmp
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Hi,
I have two Exchange 2016 servers. Ex2016-1 and Ex2016-2.
I have DNS sending mail to Ex2016-1
On the First server 'Ex2016-1, I have a third party spam application.
Up until I installed the second server, the spam software was working well. But users are telling me spam that should be being blocked, is getting to them. I checked the header on these messages and see it's coming from Ex2016-2. It's External mail.

So, first, I am confused about this. Because I have DNS pointing mail to Ex2016-1, so why is it bypassing  Ex2016-1 and going right to Ex2016-2 ?
Second, I need all the mail to route through Ex02016-1, so it will go through the spam software. What is the best way to cause this to happen,  disable the Frontend receive connector on Ex2016-2?

Thanks,
Mike
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While running a network trace for a workstation slow login issue, I notice two lines for ldap queries which failed

1)  _ldap._tcp.<SiteName>._sites.<serverName>.<DomainName>   Response: Flags:  Response, Opcode - QUERY (Standard query), AA, RD, RA, Rcode - Name Error

2)  _ldap._tcp.<ServerName>.<DomainName>  Response:  Flags:  Response, Opcode - QUERY (Standard query), AA, RD, RA, Rcode - Name Error

I do understand how the workstation DC location services finds a local DC on startup.  But confused as to why both queries list a DC specifically and do not mention msdcs??

All DNS records are present and have run dcdiag and confirmed replication is running as well.

Thoughts?
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Hello,

I'm getting the message listed in the title when trying to access a DFS share from a new subnet we created which happens to be a different subnet the one the nearest DFS server is.

So, the workstation on Subnet B is trying to access the DFS server on Subnet A.  Subnet B is a new subnet we just created.  Networking and DNS seem to be working fine to Subnet B and the workstation can access the DFS server by name using \\Servername with no issues.  It's only when using \\DFSsharedomain the issue occurs.  

I've set up a reverse DNS zone for the new subnet, ensured the workstation on the new subnet is listed in DNS and that servers and workstations can access the workstation on Subnet B both by IP and by host name.



I'm not sure what DFS needs for the workstation to access it which is what I'm stumped on.   Because the workstation is on a subnet without a DFS server and has to travel across subnets, it's not associated with a "site" and therefore all the DFS servers are showing up as referral targets whereas other workstations in the overall network only get referrals from DFS servers in their "site".  I wonder if this is the issue?

 Can any one assist?

Thank you!
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i have 1 default lan and 3 vlans.
setup on our watchgaurd firewall
vlan10 ip address 172.16.0.1/23 dhcp relay to the dns server
vlan 20 ip address 192.168.20.1/23 dhcp relay to the dns server
vlan 30 ip address 192.168.30.1/23 dhcp relay to the dns server

On the dns server i have the 3 vlans with thier own scope and in thier scope options i have the router set to
vlan 10 172.16.0.1
vlan 20 192.168.20.1
vlan 30 192.168.30.1
in the dns server routing and remote access i have the ipv4 dhcp relay agent set to 172.16.0.1, 192.168.10.1, 192.168.20.1, 192.168.30.1

all of our switches have the vlans setup also
any time i connect a pc to a switch that has its port set to any of the vlans it gives a bad ip address, 169....
anything on our defualt lan works

for a while i was getting this error on our dns server event viewer.
IPBOOTP was unable to receive an incoming message on the local interface with IP address 191.168.0.4. The data is the error code.

i restarted and also deleted and created the routing and remote acces dhcp relay agent
I dont get that error code any longer but the vlans still dont work
HELP
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We currently have our DAG setup with 2 exch 2013 servers. Right now if the dbs flips over to the passive node, we have our network guys make the switches on the routers so that it now points to the passive server instead of the one that was active, because there is only 1 outside IP address.
Now we are going to add another external IP address so that in the event the dbs ever fails over to the other server, we don't have to have the network team make any changes. They are going to set this up with the second external IP address..
My questions is, do I have to make any changes in the external dns for this to work or with the internal dns?
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Exchange 2016 on Server 2012 R2.

Exchange is working fine.

Mobile users, all on iPhone, can connect to the Exchange Server for mail when they are off site, but not while on site & connected to the LAN Wi-Fi.

If they turn Wi-Fi off, they connect (obviously via cellular)

Why can they not connet through the LAN Wi-Fi?
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I have multiple Windows 2008 domain controllers and DC have DNS and DHCP role on it. I am planning to demote one domain controller (FSMO role in another server). It has DHCP and Integrated DNS installed. What steps I needs to take to remove DNS from this server other than dcpromo?
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We have a web application that uses the client email to send email 'from'. We want to add an SPF record on the client's DNS (text records) to allow this. I need to confirm the syntax before I do so.

v=spf1 a mx a:mail.domain.com mx:domain.com ip4:XX.XX.XXX.XX ~all

Open in new window


"domain" being their domain name
XX.XX.XXX.XX being the IP of the server that hosts the web application

Please let me know if you think this looks correct or if any changes are needed.. Also what is the difference between mail.domain.com  and  domain.com
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Hi All,

I have a quick question I hope you can help me to fix.

Environment: I have an environment where I have installed a new AD and the domain name is something like corp.example.com

As a NETBIOS name during the AD install wizard I did choose "example" to make things easier and consistent with the public DNS name. The public DNS registered is example.com and there is public website running with example.com already hosted by WordPress and DNS registrar is GoDayddy.

Issue: Internal host names are not resolved properly with NSLOOKUP

1. Hostnames are working fine

2. IP Addresses are working fine

3. FQDN are NOT working fine. They are resolved with internal domain appended to external domain name.

eg. "VM1.CORP.EXAMPLE.COM" returns VM1.CORP.EXAMPLE.COM.EXAMPLE.COM and public IP Address registered with the website DNS Provider

4. FQDN with a trailing "." are working fine

eg. "VM1.CORP.EXAMPLE.COM." returns the correct IP Address as expected

Configuration: AD/DNS server is pointing at itself. NO forwarders configured. AD is pointing at an internal Gateway. This gateway is configured to talk with the internet using a different network through a separate Router connected to the internet.

My question: It's obviously not a question of routing but I dont understand why DNS forwards queries for FQDN names to external DNS servers considering that "A" and respective "PTR" records are fully registered and working on the …
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Hi,
This question is getting asked a lot from me lately and I am using my common sense to answer it, but need other opinions please.
Basically a company might have a large company name like:
http://averylargecompanynamethatisverylong.com
They may also have registered
http://asmallname.com
http://asmallnametoo.com

Now my question is more targeting to SEO.  Which domain should have their website hosted at?  Where should their emails be (as you don't want people to have to remember a really long email)

So my question is, if you have many domains for your company, which is the best one for hosting the website, and obviously the site with the smaller domain name would be best for email promoting so should you host the site at the best keyword, long domain, the have a web forwarder for all other domains, and then simply set up email hosting for the smaller domain.

I am asking from a SEO and marketing point of view.  

I think I know the answer, but I need a discussion to be sure.
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What is a quick but definite test to run from the Linux command line to check if dns requests are being hijacked. The test should not require having to change the dns servers for the device that the test is being run from.
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Using the local dns, the pinged domains result in 'Name or service not known' as expected.
I changed the dns to Googles then tried again.

# cat /etc/resolv.conf
# Generated by NetworkManager
#nameserver 192.168.1.29
#nameserver 192.168.1.30
nameserver 4.2.2.2
nameserver 8.8.8.8

# ping basxsx.com
PING basxsx.com (198.105.254.11) 56(84) bytes of data.
^C
--- basxsx.com ping statistics ---
8 packets transmitted, 0 received, 100% packet loss, time 6999ms

# ping gasxwed.com
PING gasxwed.com (198.105.254.11) 56(84) bytes of data.
^C
--- gasxwed.com ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 3999ms

The 198.105.254.11 IP seems to belong to Level 3 Communications.
What's going on?
0
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Dear Sir / Madam,

We have multiple domains.  Currently we are doing domain consolidation to have one domain.

we have migrated users and workstation from AP to AM domain.   After migration, user can login to AM domain successfully with LAN connection.   but user is having issues on printing, accessing H drive - windows prompt for login credentials. but won't accept.  cannot connect wifi.  Attached print screen.  

Can you please advise on this ?
AM-domain-issue.png
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Today we changed the DNS and MX records for my company's website and I am not sure how to confirm if we did it correctly since we are getting the Bluehost holding page. I know it can take up to 72 hours but I want to just make sure it is all in working order. However, when I run the website through intodns.com it gives me a lot of information I do not know what to do with.

The website is www.beechtreetrading.com

We bought the domain through G Suite/GoDaddy and Wix originally, and now are hoping to have the website on Wordpress as a mapped domain with Bluehost. We changed the DNS on GoDaddy to point to Bluehost and then since we have our business email set up through G Suite, we deleted the old MX Records on Wix and added the new ones.

Wordpress still says DNS configuration required and now when I try to preview the site in Wordpress it gives me this message: The webpage at https://beechtreetrading.com/?iframe=true&theme_preview=true&frame-nonce=82ddc6aeee&cachebust=0&calypso_token=c7539680-e97e-4b53-a62b-155823a59520 might be temporarily down or it may have moved permanently to a new web address.

Is everything still in the process of updating? Or is there a step we missed? Thank you in advance!
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Hi,
I'm in the middle of a migration/co-existence with 2016/2010.

I cut over the DNS settings this morning.

In the Queue viewer on the 2010 server, all looks good.
But in the Queue viewer on the 2016 server, I am seeing a large number of messages in the "site:default-first-site-name:version14" queue -- about 6,000 messages.  Last error says:
Cannot achieve Exchange Server Authentication: Last Endpoint attempted was (IP address of one of my 2010 servers).

Help please!
Not sure what to do to get this queue cleared out.
Thanks!
Nacht
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Hi,

I am migrating Ex2010 to Ex2016. They are running in co-existance mode right now.
This morning I changed the DNS settings to send my mail to the Ex2016 server.
Outlook and OWA are working fine, but users on phones/tablets are telling me that their devices keep asking for passwords and then don't accept them.
Any ideas?
Thanks,
Nacht
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Experts,

We are trying to bring up a postfix mail server on an AWS EC2 instance. We have gone through SES but we need to manage our mail server rather than AWS managing it for us.

We already have a domain linux.com. The next step would be to bring up a EC2 instance and install Postfix on it. I would assume we need an Elastic IP assigned and then map a DNS mail.linux.com to it so that is is resolvable. I'm next assuming we need to assign an MX record for mail.linux.com. Would this generally work if you send email to someone@linux.com or are there additional steps like assigning SPF records and DMARC.
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Anybody have info about hosted DNS and the Magic Quadrant? We're looking to host our public DNS.
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DNS

25K

Solutions

12

Articles & Videos

25K

Contributors

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.