Ask MetaFilter posts tagged with DNS

Why did AT&T lose our DNS records!?

kbanas — Tue, 02 Dec 2008 07:08:04 -0800

iPhones, AT&T, and the University of Michigan..?! Help me sort out what is a - best I can figure - DNS issue! I will attempt to be brief and only cover the salient details.

I work for the EECS Department at the University of Michigan doing IT support. I am the desktop support guy. In our department we also run our own web and e-mail services (and servers). I don't have much to do with this - these are all rack mounted Linux machines and they're administered by a bunch of Unix people. I am, I guess, sort of a filter between these cantankerous admins and the general population. Admins change the mail configuration. It breaks Outlook. I figure out how and why it fixes Outlook. They claim people should just use Berkley Mail. I politely disagree. We eventually reach compromise.

Anyway. I have an iPhone, as do several faculty, staff and graduate students in the department. I use this phone with my EECS IMAP mail server. This has never been a problem for me.

Then, suddenly, last week I could no longer send or receive e-mail from my EECS mail account while on the AT&T network. It would work on the campus WiFi. It would work on my WiFi at home. It would work at random WiFi hotspots. But it refused to work while using 3G (or EDGE) data services.

My GMail account worked without issue.

Well, I figured this was just a transient issue and it would disappear.

No such luck.

Instead, starting yesterday my trouble ticket system started to fill up with complaints from other iPhone users that their EECS mail is also not functioning on the cellular network.

At this point, I started to do some digging.

It seems like the AT&T network has, like - and here I lose the technical language a little bit - lost our DNS entries.

I installed an SSH client on my iPhone and on the 3G network I can't connect to one of our machines - marquette.eecs.umich.edu - I get a "hostname not found" error. But, if I try it via IP, it works.

I tried to browse to our website, www.eecs.umich.edu, on Safari. On the 3G network, it can't open the page. If I try it via IP, it works.

I went into my mail client and changed my incoming and outgoing mail servers to IP values instead of hostnames, and, viola, on 3G it started to work.

What the hell?

Our admins don't have a clue. They say our MX records and our servers and our firewalls are all configured correctly. They look at the logs and, yes, as you would suspect (as the names can't be resolved), they don't even see my phone attempting a connection.

Data points I think would be helpful - is this a geographical issue? Can people in other parts of the country with iPhones browse to, say, www.eecs.umich.edu? Is this an iPhone specific issue? I've read some criticism of the iPhone's DNS resolver - does this affect other mobile devices on the AT&T network?

That settled, what the hell could be causing this? I have no idea who in AT&T I would possibly call - it sounds like the support call from hell. I have a hard enough time just trying to check how many minutes I've used.

Any ideas, hive mind?

DNS for just the office ?

southof40 — Thu, 13 Nov 2008 17:07:53 -0800

What is the best solution to provide 'local DNS' for an office which has outgrown a hosts file solution ? We have a domain, say foo.com. We use ZoneEdit to provide DNS for the domain (including numerous sub-domains).

Within the office to allow machines/applications to be named we have used hosts file but this is no longer practicable (unless there's some means of automating hosts distribution).

All machines in the office are using 192.168.10.x IP's and, I presume, this means that we couldn't put the sub-domains on ZoneEdit even if we wanted to.

I feel like we should be able to run a DNS server which the local machines can use as a 'DNS server of first-resort' and then if the name is not resolved the DNS request can go onto our standard DNS servers which will resolve everything that isn't resolved by the 'office DNS' server. Hence onlyforuseintheoffice.foo.com would be resolved to 192.168.10.1 but thewholeworldneedsthis.com would not be known to the local DNS server and would go out to the I'net to get resolved (by virtue of the ZoneEdit servers)

Finally the question(s) !

1. Can we 'split' responsibility for the domain in this way ?
2. There's 'Simple DNS Plus' and there's the stuff that's built into Window 2003 - any experiences of doing what I describe with either ?
3. Is there a simpler 'non-DNS server' way I've overlooked ?

What happened to the Internet in 11/07?

about_time — Fri, 07 Nov 2008 09:15:40 -0800

A question about Internet domains and DNS: What happened to the number of registered domains between 10/07 and 11/07? For the first time they dropped, and significantly: 2 million domains were unregistered. Zooknic shows this result.

Date Total domains
11/15/2007 94,854,717
10/15/2007 96,946,506
9/15/2007 95,233,625

This is the only month in history that there is negative growth since 1998. Was there a policy change? Something cleaned up? If you know of something, a specific reference to what you recall would be great to have. Thanks.

How do you spell D-N-S?

fijiwriter — Tue, 16 Sep 2008 07:54:32 -0800

How do you explain DNS, A records, MX records, etc. to your staff and clients? What's the best way to get non-technical people to understand this? In my line of work, we have new co-workers who know just a little bit of what DNS is. Usually, it's their understanding of how a person finds a website or gets email to someone. And that's pretty much it.

So, I'm considering a primer of what DNS is, what it does, why it's important, what role A/MX/www records play, and the like.

What have you seen online, preferably with graphics, that you've used to explain to people what's going on in such a foreign concept? Or, how have you explained this subject?

Yes, I know there are Internet for Idiots-type books out there and Wikipedia entries, but that is a Step 3, and we're just on Step 1.

Who to file a complaint with for a problem with a US locality domain registrar?

Anonymous — Tue, 09 Sep 2008 11:34:27 -0800

Who is the appropriate party to file a complaint with, for a problem with a US locality (*.portland.or.us, NOT *.us) domain registrar that is not updating DNS records as requested? Five years ago or so, it took over a year (not joking...) for the registrar update my DNS records and only after numerous emails, faxes, and letters. Time to move servers again, and I've already waited over a month with no results. The registrar's website says they are going to start charging for this wonderful service next year. Who can I complain to about their current service so I might see some action taken on my DNS request; who can I complain to to suggest *.portland.or.us domains be moved to another registrar?

CNAME a domain and delegate the subdomain

qvantamon — Fri, 29 Aug 2008 13:33:35 -0800

Can I CNAME a second-level domain, and delegate a subdomain to a nameserver? What if the nameserver is the same for both? So here's my problem: I have a page at example.freehost.com, and I want to:
1) Buy domain example.com and forward (www.)example.com to example.freehost.com via CNAME.
2) Buy hosting for a subpart of the site (say, forum.example.com), in a host that uses cPanel (which means I should be able to delegate NS for forum.example.com to them).

The added complication is that I want to buy the domain and the hosting from the same company, which means the nameserver for forum.example.com could end up being the same as the one for example.com

So, in summary I want to have entries like these:

example.com CNAME example.freehost.com
www.example.com CNAME example.freehost.com
forum.example.com NS 1.1.1.1
forum.example.com NS 1.1.1.2

And on 1.1.1.1 & 1.1.1.2, the normal cpanel entries...
forum.example.com A [myhostsip]
forum.example.com MX [myhostsip]
blah blah blah etc etc.

My first question is - Is that a valid configuration (cnaming the second-level and delegating the third level)

My second question is: can I have both entries in 1.1.1.1 & 1.1.1.2 (that is, have the NS entry be a self-reference)?

Or will this self-reference make the internets asplode?

Also, if I can, will I be able to do it by just managing my DNS entries, and asking the hosting guys to put forum.example.com on cPanel, or will this require some black magic in part of the hosts? (which means they probably won't do, since I'm aiming for a cheap host)

.int needs a .com FQDN set up. Who in the what now?

bartleby — Mon, 11 Aug 2008 09:42:05 -0800

DNSfilter: Trying to help some folks install new software, which requires a FQDN to run its server component. But their domain is an .int domain (they're not sure how they ended up with that, not being an NGO) which won't work. So I'm stuck guessing how to get a folks.com FQDN set up under folks.int. Can you point me at some resources? So:
1) how would they have ended up with a .int TLD? They're not working for the UN or anything.

2) this is new to me, and my guesses seem to be wrong or uninformed.
Server 2003, domain controller, went into DNS settings, Forward lookup zones, trying to create an Alias CNAME, not working so well.

It can't be very hard, but they kind of need it Now, so I'm stuck not knowing much DNS magic and not much time to learn.

Why does my web site show up for everyone but me?

bflora — Sat, 19 Jul 2008 10:56:28 -0800

I've got a web site that shows up just fine for everyone except me. I get a big fat "page not found" when I navigate to it even though it works fine in proxy browsers, I've used ipconfig/flushdns and cleared my browser cache. I'm sure it's a DNS issue of some sort, but have no idea what else to do. Help?

Free linux dynamic dns hosting?

Thoth — Mon, 16 Jun 2008 08:39:35 -0800

What is the best Linux friendly free dynamic DNS hosting provider? I'm in the process of setting up a server at home that I would like to access from work etc, so I'm after a good free dns service that features an automatic update client which runs reliably on Linux.

A google search of "dynamic dns" and many other permutations thereof throws up what seems to be about a million "free" dns providers, so I would be eager to find out if there is any consensus on what's good out there.

Thanks very much!

ISP hijacks invalid URLs—sometimes

adamrice — Tue, 22 Apr 2008 09:37:11 -0800

NetworkFilter: I have a bizarre and arcane-seeming problem with my home network, the Internet, and my ISP's DNS. Invalid URLs are being redirected to the ISP's search page—in some cases. If I type in a partial URL like "amazon", normally I'd expect my browser to figure out that I meant amazon.com and go there. And indeed, it worked that way until about two weeks ago.

At that point (with no changes at my end), I started getting redirected to a special page run by my ISP (grandecom.com) that attempts to monetize my laziness by showing me ads. I realize there's been a lot of this kind of thing with a lot of different ISPs lately.

I have two Macs running 10.5, connected via cat-5, and one Mac running 10.4 connected via wifi, all running into the same old-ish Netgear router (which has current firmware). What I've just figured out is that the wifi-connected Mac does not encounter this redirect; when I connect any of my computers directly to the cable modem, I also don't encounter it.

I've spoken to my ISP's tech support a couple of times. One guy had never even heard of this redirect page and expressed surprise that it exists. The other had heard of it, but claimed there hadn't been a lot of complaints relating to it. And because the problem went away when I took my router out of the loop, he's inclined to blame it.

Clearly the ISP's DNS is implicated, and I am not satisfied with this response, or lack of solution. I'm wondering if anyone has encountered anything like this, or can shed light on it.

need help with receiving emails from outside domains on exchange server 2003

antisocialiting — Mon, 14 Apr 2008 09:32:02 -0800

How to set up MX records on on a DDNS server (zone edit to receive outside domains email) I have a Win2k3 server with exchange server installed on it. I use a ddns system (zone edit.com)because my isp is comcast and its just a small home server. I am able to send and receive internal emails with no problem. I am able to send to out side domains like gmail and yahoo but if I try and reply to them I get non delivery notifications. My question is 1st. what should be the mx record I use for zone edit if I should use that at all. 2nd do I need to make changes to my dns server like add reverse look up? 3rd is this something I should set up directly on the exchange server and if so what. any links to wlakthroughs etc would be very helpful. thank you in advance for any help.

Why Am I getting 404 errors for legitimate web pages while casually browsing?

smersh — Sat, 12 Apr 2008 01:58:12 -0800

While casually surfing, why am I getting 404 errors for pages that definitely exist (like google and facebook)? How can I stop it? While casually surfing, I get at least five Hostgator 404 errors a day, for pages that definitely exist. Pages on google, on major websites like ign.com, facebook, etc.

I'm in India, surfing on a MacBook Pro, Safari, Leopard (though I've seen it on Firefox and on OS 10.4). I think it has to do with my ISP, but I'm not sure. It could be my wireless router (Airport Express).

My annoying remedy is to change my DNS Server information to OpenDNS when a page doesn't work (208.67.222.222 and 208.67.220.220). But, I get the same 404 page errors at the same frequency.

The switching of DNS servers ALWAYS helps immediately, but never long term. That is, it'll allow me to see the page/site right away, but another legitimate page will give me a 404 some time later.

Please help me. I'm really hoping that my configurations are doing this somehow, but I don't know how.

thanks!

What lies between my browser and the internet?

miniape — Wed, 02 Apr 2008 22:11:24 -0800

I have an idea for a simple piece of software. It would involve intercepting browser requests, checking the requested url (probably not ip address, so before that conversion takes place) testing the url and redirecting if it passes the test. The test will itself make a network connection. Probably a pretty simple problem, but my background is in web development, and I'm foggy about 'OS' stuff, if that's even what it's called.

How are some ways I can go about this? I'd ideally like to write the program in Java or Python, but I'm not really looking for code specific information. I'm looking for google terms, useful libraries, descriptions of what happens step by step between the time I press enter on the keyboard and the time the request leaves the computer, generally strategies.

I'm guessing it might be hard because this is what a lot of spyware does, but I would be happy even if installation required some configuration.

Don't need a cure for insomnia

whoojemaflip — Thu, 27 Mar 2008 06:39:42 -0800

Need recommendations for an everyman's guide to the DNS system thats readable yet thorough. I've recently promoted myself to boss of my own tinterweb services company, which is great on the whole However I've come to realise that my sysadmin skills could do with some polish and one of the areas thats lacking is my understanding of DNS and IP routing.

Any suggestions for a book / course / online resource that could help me make sense of it all? I do *nix and windows, which complicates things no end.

Ultimately certification would be a bonus, but I'm not sure if I want to put myself through another MCP right now.. their just so ... dull!

SOL on rDNS?

tcv — Sun, 02 Mar 2008 12:38:23 -0800

My company can't send messages to some larger ISPs due to reverse DNS not being setup. But we're in a situation that isn't so easy to solve... My company leases space in a building. The company shares a single public IP with all the other businesses. Over the last couple of years, it's become increasingly more important to make sure that reverse DNS is set up properly in order to send email over the Internet, especially to large ISPs like ATT.

Since all the companies share a single public IP, I believe that a simple call to the ISP that services the building will not work here we would, in essence, be usurping any of the other IP-sharinf companies ability to set up reverse IP for themselves.

So, what are we to do? If we can't setup reverse DNS this way, is there another way to do it so we can get around this increasingly necessary requirement?

For what it's worth, we run a Windows server.

Help solve my DNS woes

puffin — Mon, 25 Feb 2008 10:57:01 -0800

Help me figure out this DNS problem with my website... My friend has a VPS, and has very kindly offered to host my website. So far I have copied over my entire home folder from my old host (through Cpanel) to his server. I can successfully access it when point my browser to the new server's IP address (http://208.79.232.248/~crumb). I also changed the name servers over, and this change is reflected when I do a whois search for my domain. But something seems to be amiss, because when I go to my domain (crumb.cc), nothing loads. When I use Cpanel's Network Tools to check the domain, I get an "Host crumb.cc not found: 2(SERVFAIL)" error message. It seems like the name is just not connecting with the new IP address, despite the fact that I have changed the name servers and that Cpanel even lists "crumb.cc" as the main domain.

Is there something obvious that we should check? What could be the problem? Neither my friend know much about how DNS and name servers work. Also, my registrar is GoDaddy, if it makes any difference.

WIll multiple domains make any website faster?

braintoast — Thu, 07 Feb 2008 23:44:59 -0800

Will serving images, other files, etc. from more than one domain make an appreciable difference in load time? I have an html page that loads in 12 images (6 at ~25k each and 6 at ~5k each). There's also associated CSS, javascript, etc. I know that browsers are typically set to load only a couple of resources from the same domain concurrently.

I want to know if I should expect to see a noticeable difference in how quickly the page loads and/or renders if I serve the files from a few different host names. I'm thinking the time and resources for the additional DNS lookups might use up any possible gains. Anyone have more info?

DNS set up

lazaruslong — Tue, 05 Feb 2008 10:09:30 -0800

I need help setting up email addresses and DNS service for a business. So. My employer really wants email addresses for @thecompanyname.com

This is what I have already done:

Purchased the domain name they wanted from go daddy.

Set up with Bell South lots of stuff: We have the small business DSL package so we get a few free static IP addresses. I've set that up and have received the address we were assigned. Now I need to set up the DNS to point at our domain, right?

I logged into the dns management and added the domain. Now I need to figure out how to list bell south as the Primary DNS on Godaddy, right? And then set up the email addresses, I imagine using MX records (although I don't really know what those are)

Did I miss any steps? What else do I need to do? Can anyone with experience with the fastaccess.com/dns GUI from BellSouth and GoDaddy walk me through the rest? I've run out of knowledge.

Setting up subdomains for a LAN?

unSane — Sat, 26 Jan 2008 07:37:22 -0800

How do I give my computers subdomain names on my local network? For example, mylaptop.mynetwork.com, mydesktop.mynetwork.com, momslaptop.mynetwork.com, kids.mynetwork.com and so on? Do I have to set up some kind of local DNS or is there an easier way to do it in the router? I am not concerned at this point about being able to access the subdomains from the WAN although that would be handy later. It's the LAN I'm interested in. (Obviously I am using Bonjour right now but for I want to use the subdomains too). I own mynetwork.com and it points to a static IP. My LAN router is firewalled behind that. It's a WRT54G running DD-WRT. I have a spare computer I could run DNS on but I'd rather not have to do that. Everything is Macs running OS X, mostly Leopard.

How do you make a subdomain forward to a different host?

tracert — Fri, 16 Nov 2007 16:07:45 -0800

How do you assign a subdomain to a different host? So, here's an odd situation.

My brother runs a small charity that has a website at www.mybrotherschairty.org. The site is being hosted for free by a friend of his, but we don't have much contact with them, and I'm reluctant to ask them for favours. The domain name is registered with Godaddy, and while I have access to domain management there, I don't have any access to the hosting provider.

I have been asked to set up a Movable Type blog for the site, but I don't have permissions to create a new database on our hosting provider, and I don't want to jam a bunch of tables into the ones we have. Therefore, I have agreed to host the blog at my personal server at www.myserver.net/blog. I have complete control of everything related to my server, including DNS.

Okay, so what I want to do is to have the subdomain blog.mybrotherschairty.org go to myserver.net/blog. But I want to use masking so that the url doesn't change for visitors who will have no idea what myserver.net is. Yesterday, I went to Godaddy and added a subdomain though the interface there. However it's been over 28 hours and nslookup on blog.mybrotherschairty.com still says "no answer", so I think I need to do something else.

This should be pretty easy to do, I think, but I have no idea how DNS works, or what a CNAME record is, or how to bake a delicious pie with said record. Please talk to me like I'm an idiot. What, exactly, should I do to make this work?

Why does my Firefox lose its ability to do DNS lookups?

dfan — Fri, 26 Oct 2007 13:32:38 -0800

Every once in a while (time between failures ranges from 1 hour to a few days), Firefox on my laptop suddenly and permanently (until reboot) loses its ability to do DNS lookups. Every page comes up with "Firefox can't find the server at www.foo.com." Other apps (and computers on the network) continue to work fine. It seems random; I haven't been able to correlate it with anything else on the machine. Closing and restarting Firefox doesn't restore its DNS lookup ability, but rebooting does. Googling only turned up the advice to disable IPv6, which didn't help. I'm currently running Firefox 2.0.0.8 on a Dell Inspiron 8600 running XP Home, but it's been an issue since at least 1.5. My only extension is Better Gmail, and I've tried disabling all extensions in the past. I'm at my wit's end - do any geniuses here have a clue?

Help me test the waters with Google Apps

edjusted — Sat, 13 Oct 2007 20:31:17 -0800

I'm trying to set up Google Apps Email Premiere for just a few users for testing. I'm following the instructions on the Pilot program help page, and I'm not sure what I'm doing wrong. The help page says to "Add another destination". My domain is currently being hosted by Bluehost if that makes any difference. The POP server address is mail.domain.com and when I try to add that as the additional destination, it states that the setting is saved, but then it doesn't show up. I e-mailed Google Apps support, and got this back, which doesn't seem to make sense.

"I've investigated your report and found that your CNAME record isn't configured properly.

Here's the current CNAME record:

Non-authoritative answer: mail.domain.com canonical name = domain.com.

To fix this issue, please modify your CNAME record as follows: mail.domain.com points to ghs.google.com"

I'm not a DNS expert, so I may be wrong, but this is what I'm afraid of:
1. change CNAME record to ghs.google.com
2. doh...all the e-mail sent to the rest of our accounts *not* on the Pilot program don't get delivered
3. once the ghs.google.com CNAME record gets propogated, then I do the "Add another destination"
4. add the MX records for Google mail
5. doh...while the MX records propogate, the people *on* the Pilot program don't get their email

What am I missing? Can someone help me with a more detailed step-by- step of what I need to do to make this work?

Email blocking, the "MX preference record", and snooty techs...

gemmy — Tue, 25 Sep 2007 22:20:02 -0800

I work for a tiny non-profit where I'm the "IT department" by default. Trying to investigate further why our website/emails are being blocked by certain of our clients/relationships/partners, and I'm hopelessly in need of some guidance. Although I'm generally tech savvy enough to deal with most of the IT issues around the (3-person) office, I'm pretty much stumped. Trying to read up on the issue isn't helping much, and I want to know more so I can decide what to do.

Problem:
Recently, some of our relationships have complained that our website is being blocked, and in some cases emails from us won't go through. I made some direct inquiries to the IT staff of the affected organizations, and in all but a few cases we were able to easily solve the problem - using whitelists mostly. But there are still a few very important exceptions, and they concern me.

Basic Setup:
Our primary domain is registered at and hosted by catalog.com/webhero.com [I know, I know. Set up BCS - before current staff.] Our very few (5 or so total) POP3 mailboxes are also hosted by them. We send our mail through the SMTP server at our ISP - Speakeasy. Fairly simple and straightforward.

Here is the gist of what I was told by an Information Assurance tech in one of the offices who do not have access to our website and can't receive our emails:
Your domain is aliased to the catalog.com domain, and we are currently blocking catalog.com domain traffic for security reasons because the domain has been suspicious for malware, SPAM and phishing traffic. Since catalog.com and your domain are registered under the same IP group, it will be difficult to whitelist just you, since you are using the same DNS as the other registered folks in the catalog.com IP/domain that sends out SPAM, phishing and malicious malware to the Internet. We are not targeting your domain for the problem, it is just that you are registered behind an untrusted catalog.com domain. This was then followed by a suggestion to switch web hosts.

Question 1 (a,b,c, etc.):
For three years, I have monitored - on a bi-monthly basis or so - all the IP addresses in the MX record for our domain on various RBL/DNSBL, as well as against the Bleeding Edge BlackHole DNS list and list of "Known Compromised Hosts". From what I have gathered, I disagree with their assessment of catalog.com/webhero.com. But it's entirely possible that I'm wrong. What evidence is there to support this claim above of catalog.com needing to be blocked? I don't even know enough to say that his explanation sounds plausible - is it? What else should I be doing to check for possible issues cropping up with my domain registrar/web host?

Question 2:
Given their block of all things catalog.com, is it normal that it would also affect an email that we send to them through the Speakeasy SMTP server? I understand that the catalog.com domain/IP addresses are tied to the "MX preference record" for our domain name. So because our domain name is included in the "sent from" headers in the email, it ties the email to our domain name, ties it on to the catalog.com domain/IP addresses, and therefore the email gets blocked?
That logic seems really weird to me. Say that someone spoofs the "from" header, pretending to be from a user at my domain. Would that email then be blocked too? Or if I change my "from" information in Outlook to a different domain, would the email then be able to go through? I was under the impression that the server that the email actually comes from matters, doesn't it?

My non-profit is tiny, but has a big footprint in the specific community where we work. We deal with a number of very large and security-conscious organizations and with the U.S. government. This is merely an annoyance right now, easy enough to work around, but it could become a real issue for us moving forward. I want to try to understand what is happening and what we can do about it. Catalog.com/Webhero.com have been great to us over the last six years or so. Is switching web host really going to make a difference? Aren't most web host susceptible to these kinds of issues?

Any thoughts, help, or suggestions you would be willing to offer would be much appreciated. Thanks!

How to not use VPN's DNS on OS X?

dmd — Tue, 11 Sep 2007 06:52:07 -0800

When I connect to my VPN in OS X (using the built-in client), all DNS requests are sent through the VPN. How can I prevent this? I have the checkbox "send all traffic through VPN connection" unchecked, so I can use the internet and the VPN at the same time. However, once I'm connected to the VPN, DNS goes through the VPN, which makes everything horrifically slow. I'd like to have my DNS servers remain unchanged. All the sites I access on the VPN are in my /etc/hosts, so I don't need the VPN's (very slow) DNS servers.

Is there something I can do at the command line maybe to change the DNS servers back after connecting?

How to query lots of DNS records

TungstenChef — Wed, 05 Sep 2007 16:59:10 -0800

50 domains, 3 registrars, and DNS records hosted at 6 different providers. I need help inventorying this mess! I've been given the task of inventorying our domain name situation so that we can make it a little less insane. So far I've been able to collect all the domain names and their nameservers into an Excel document. What I want to do next is get all the DNS records (hopefully) or at least the A, NS, and MX in a format that I can easily bring them into Excel. Ideally I'd like to run a batch or script to do this all at once, but my limited knowledge of nslookup and dig has failed me. Help me hive mind!