I love them both, goddamit!
November 14, 2007 1:36 AM   Subscribe

Can someone explain in plain terms why a Mac laptop is able to connect with no configuration required to a network, when a Windows laptop (one XP, one Vista) just will not?

I'm sure there is an easy explanation for this, but I don't understand what it could be...

This question applies to two different and separate locations; one, at work, and two, at a different locations' wireless network.

A) The wireless network:

A local business (PC) offers WiFi connectivity - this is accessed by the browser on the PC being shown a 'login' type page provided by the server(?) when the browser tries to access an internet address. You then must enter ID and password, and receive a 'logged in' message and can thus re-enter the URL you want and off you go - pretty standard stuff.


All of the above happens with a laptop running XP / Vista perfectly. If you use a Macbook though, what happens is that you enter a URL that you want, and poof! there is is. No login screen or anything.

QpartA) So how on earth does that happen?

B) At work, there is a network that all the PCs use. I plug in the MacBook, and it allows me to connect to the internet with no difficulties. (Not the work intranet stuff, just the www, which is all I need)

If I connect the XP/Vista laptop though, it connects to the network, but will *not* access the internet; sometimes it says 'Gateway not found' and when trying to reset the adapter, it says 'Unable to contact your DHCP server'

QpartB) So how on earth does that happen?

In summary; Why does the Mac just 'do it' and how do I get the Vista laptop to do the same??

(And the first person that says 'just use the Mac' loses a testicle:) I love 'em both, godammit!)
posted by DrtyBlvd to Computers & Internet (8 answers total) 2 users marked this as a favorite
Part a: I can see at least 2 ways this could happen. Both are misconfigurations of the wireless network (or easier/cheaper ways of setting up wireless access).

They would have to have the router for the wireless network poorly configured in both these cases. Allowing all traffic from any mac address to access the internet at large.

1) They are using an "automatically detected proxy" as their protection and way to gain money. As such majority of windows machines will automatically use the proxy and the proxy has the magic user/pass page, but the browsers on Mac OS X used to (still?) cant automatically detect these, they certainly dont do it by default. This used to be a pain for me on my old corporate network I had to constantly figure out and update the proxy information. (this would mean both email and IM should still work on the PC without the user/pass is this correct?)

2) The second is they are using a custom dns (name server) server (which is returned in the dhcp lookup) but your macintosh is ignoring due it having a dns hard wired into its setup already. The dns checks for a particular IP (or one hopes mac) address that is making the request, if it is authorised it returns the true IP address of the URL if not then it returns the local webservers address ... which throws up the login page.

Neither of these is the correct strategy. What they should have is a smarter router. This router should detect if the mac address is authorized if so it lets through the tcp stream or udp packets. If not it hijacks any http packets and sends them to the login page on a local webserver and drops all other type of outbound packets until that mac address is authorised. This is not easy to setup but I am surprised that there are not more "out of the box" solutions that do this.

My brain isnt up to handling part b tonight. Basically there is too much information missing to fully answer either part of the question well but hopefully I have sparked off some ideas for differences in settings you can look at.
posted by Gilgad at 2:16 AM on November 14, 2007

The technique to force a user through a login page (or any other page) is known as "Captive Portal". Modern implementations can and will force you through the page, regardless of your settings.

But, I'd go along with Gilgad's suggestion, namely that it's a mis- or poor configuration, look up "naive implementation" from this page:

Wikipedia article on captive portals
posted by phax at 2:47 AM on November 14, 2007

Response by poster: Thanks for your response - So "automatic detecting' of proxy is the key if I understand correctly?

IE If I can get the Vista box to *not* "auto detect" any proxy, then it should work like the Mac, at both locations?

I follow your reasoning re. 'smarter router', and am surprised that it isn't a de facto.
posted by DrtyBlvd at 2:58 AM on November 14, 2007

You can try to set the DNS settings manually for your wireless configuration (i.e., not let the WiFi access point give them to you via DHCP) and Internet Explorer at least used to have a proxy setting which let you either to use no proxy, autodetect or manual setting.

If you don't use IE, Firefox has this for sure.
posted by phax at 3:18 AM on November 14, 2007

And oh, by the way, Macs don't have the DNS settings hardwired by default, they will accept the DNS settings doled out by a DHCP server. This can be of course overridden.
posted by phax at 3:21 AM on November 14, 2007

Part A sounds like a stupidly-designed captive portal; you ought to be able to get your PC to work like the Mac (apparently is) by disabling Proxy settings, and manually setting your DNS servers. You could use the DNS servers from OpenDNS, if you want.

There are lots of ways of doing captive portals; they're doing something that's crummy and only works on PCs. Their stupidity is the Mac users' gain in that case.

Part B is a bit more complex. I'm not sure what the deal might be, but it sounds like you're using a DHCP server that doesn't like the Windows clients but works okay with the Mac. I have heard some bad things about Windows' DHCP client implementation (specifically, that it doesn't like to release addresses), so it doesn't strike me as impossible that it might get into a fight with a router.

You might want to look at this page; apparently there are some known bugs with patches.
posted by Kadin2048 at 8:15 AM on November 14, 2007

The DHCP issue in the second situation sounds similar to a thread I found a while back on digg about a swedish ISP's servers can't work with vista's DHCP client.

My understanding of it is Vista is using an old form of the DHCP broadcast flag, which a lot of folks have not bother implementing, while it is technically part of the standard.

There is a knowledge base article about it here:
posted by mrzarquon at 6:09 PM on November 15, 2007

Response by poster: All - Thank you for your suggestions and replies...

Part A) - OK, got that - I can have a play next time I am in situ and see what happens with disabled proxy settings.

Part B) - Sort of OK, got that, but not really...

Having read the XP link from Kadin, it doesn't seem relative to Vista at all (or am I missing it?) and the second link from mrzarquon advises registry changes to a key that I actually don't appear to have(!) (Specifically the {GUID} reference) which puzzles me greatly - the article appears to read as though I *should* have the key, so I'm puzzled again.

I had anticipated a 'straight forward' (I know, I know) Mac does it because of 'X' kind of reply - which, really, Part A) actually *is*.

Part B) has developed rapidly into a networking functionality question that is now succesfully annoying the beejesus out of me.
posted by DrtyBlvd at 2:16 AM on November 20, 2007

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