Wikipedia:Reference desk/Archives/Computing/2007 June 24

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June 24

Linking a domain name and an IP address

I have an IP and DNS addresses for a local DSL Internet connection. I know I can point a domain name at the DNS addresses but is it necessary for the ISP to add the domain name to the DNS table so that the domain name is linked to the IP address? 71.100.3.132 00:08, 24 June 2007 (UTC)

Most domain name registrars will ask you to give them your IP address, which is then linked to your domain in their nameservers' tables. The only time your ISP would be involved in the process is if you were purchasing the domain from them. Shadow1 (talk) 12:51, 24 June 2007 (UTC)

Just nitpicking... The registrars ask for your DNS server's IP address, not your IP address. Your DNS is what maps the domain name to your IP address. If you do not have a DNS server, you will need to get one (or create one - which is a pain). There are many cheap/free DNS services on the web. Some even allow for roaming IP addresses, just in case your ISP changes your IP address on you. Youth in Asia 13:08, 24 June 2007 (UTC)

Okay how does the domain name know which IP address in the DNS belongs to you? Does it link to it automatically using the IP address your are connecting from to do the domain/DNS setup? 71.100.3.132 18:59, 24 June 2007 (UTC)

A DNS service is specifically designed to take a domain name and return an IP address. It is your job to tell the DNS server what the IP address is for each domain name. When you hire a DNS server (I use secure.net), you have to say, "I just got superglobalmegamax.com and I want it to point to 64.23.54.2." Then, you tell the registrar what your DNS service's IP address is. When joe schmo types in superglobalmegamax, they will initially get the DNS server IP (ie, secure.net) and then the DNS will tell them the IP. Nameservers - the one that talks to the DNS - will commonly cache requests so it doesn't have to go to the DNS every time you type in the same domain name. You can even cache lookups on your local computer to speed things up further. Youth in Asia 19:59, 24 June 2007 (UTC)

Keep in mind that if you do not work with your ISP, that they probably have a PTR_record#Types_of_DNS_records for the IP provided to you, so any time a third party tries to resolve the IP, they'll get the hostname the ISP defined, not your domain name. You'll have to get your ISP involved if you don't like that. -- JSBillings 16:31, 25 June 2007 (UTC)

Two NAT related questions

Dear Wikipedians:

I have 2 NAT related questions for which I cannot find answers in Wikipedia's NAT page.

Question 1: If NAT disrupts end-to-end connectivity, then how is it possible for me to initiate an MSN conversation to my friend and to have her see my first message popping up on her computer when both of us are behind our respective ISP's NAT (i.e. worst-case NAT scenario: both ends behind NAT). And how can I use the "MSN" principle to visit her personal IIS web server she has hosted on her MSN computer?

Question 2: How long does NAT keep a (internal IP, internal port -> external IP, external port) mapping available in its memory?

Regards,

76.65.14.155 01:17, 24 June 2007 (UTC)

For the first question, you and your friend are not directly connected to each other. Instead, your MSN clients are both connected to a central server, which relays messages between you two. Not sure about using the "MSN" principle, though your friend should port forward in her router. Second question, dunno. :) Splintercellguy 01:53, 24 June 2007 (UTC)

Thanks for reply. By "MSN" principle I mean can I call up her personal IIS web server in the same way that I call up her MSN messenger? Particularly if she couldn't do any port forwarding because she has an extremely nasty ISP (like Rogers in Canada) that dumps all of its non-business customers into these NAT pig-pens and refuse them any access to the routers? (But even for my friends who are imprisoned behind Rogers evil NAT I could still initiate connection to their MSN messengers). 76.65.14.7 05:04, 24 June 2007 (UTC)

A kinda bulky and impractical way I can think of top of my head would be for your friend to host the IIS server as a Tor hidden service. Splintercellguy 06:52, 24 June 2007 (UTC)

A less bulky and impractical way would be to use IPv6 on both machines, either using Teredo or another tunnel broker. That way, both machines would get a real IP address, and you could do anything you would normally do with a real IP address. --cesarb 11:50, 24 June 2007 (UTC)

huaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa! That is juuuuuuuuuuust what I'm looking for. Thanks a lot cesar and splintercellguy! 76.65.13.119 15:46, 24 June 2007 (UTC)

Is Steam adjusting prices for me based on where I live?

Does Steam automatically convert the listed prices to Canadian dollars, Australian dollars, etc if you browse it from Canada, Australia? On its front page, http://www.steampowered.com/v/index.php , Dark Messiah and Thief are both listed as $19.95. Is it the same for everyone else? 202.10.86.63 17:38, 24 June 2007 (UTC)

I was just reading this the other day- short answer is that no that's USD --froth^t 18:07, 24 June 2007 (UTC)

Linux root filesystem

Can linux at boot time use smbfs as its root filesystem? Can it use image file stored in smbfs as root filesystem (this would be more important)? (It would make possible booting linux from network (using windows server with tftpd32 and somewhere shared (over smb) root filesystem image)). Articles linux kernel and Linux Startup Process did not contain information about root filesystem mounting. initrd has data about use of plain NFS as root FS, but no data about SMB or SMB/loop -Yyy 19:34, 24 June 2007 (UTC)

No - a minimum of the Linux Image and GRUB would need to be on a filesystem GRUB can understand. You might be able to symlink some of the other folders away to SMB. --h2g2bob (talk) 01:47, 25 June 2007 (UTC)

Actually, you don't even need GRUB (you can network boot, which is what is being asked about). As to using CIFS as the root filesystem, I don't think anyone ever tried that; it should be possible in theory, as long as you used a Samba server correctly configured to use POSIX permissions with the Linux client. You could also in theory use a loopback image from a Windows server (but it wouldn't be similar to NFS root then, since the root image would have to either be not shared or not writable). --cesarb 09:54, 25 June 2007 (UTC)

Yes, i have been able to load kernel through tftp, there probably is possible to use ramdisk as root FS (image loaded through tftp), but it would be inefficient. I intend to use loopback image from a Windows server. Limitations are acceptable (for example ability to boot knoppix (or something similar) to real hardware (not vmware or something similar) without ever writing a physical CD). Thanks for the answer, this question reduces to configuration of initrd to: load network card driver module; load CIFS module; get IP adress from DHCP; mount SMB share into initrd filesystem; mount root filesystem image over /dev/loop (at the end to be moved over to /). -Yyy 15:30, 25 June 2007 (UTC)

Lightbulb from PC

I hooked up a lightbulb to my computer but it won't turn on and I don't know why.--71.185.138.224 23:16, 24 June 2007 (UTC)

Last I heard, PCs don't have lightbulb sockets, so I think we need more information. Is it a USB light? A special device (such as some sort of electronics kit)? A 50-year-old valve-powered computer? Confusing Manifestation 23:30, 24 June 2007 (UTC)

X10? —Steve Summit (talk) 02:42, 25 June 2007 (UTC)