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Networking help for a noob

lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
Hi, all, I've got a router issue, and as someone with no network engineering experience I thought I'd come here to ask for help.

My partner and I both work from home. We have a modem provided by our cable provider, and attached to that we have an Airport Extreme. Her computer is connected to the Airport by wire, the rest of the house is serviced wirelessly. Her employer asked us to make a change to our subnet, and this is where it begins.

Using the Airport Utility, I could not find any way to directly alter the subnet. So I called our internet provider and they told me that, according to my account, since I was not using the wireless functionality in their device, that all routing functions were turned off, and control was given over to my own router (i.e. the Airport Extreme).

The modem/router has one input (ADSL from the provider), and four LAN outputs. One is specifically used for Internet traffic, and that connects to the Airport Extreme's WAN port. The other three are for video signals; one of them is being used to route to our TV box. This info all comes from my provider.

So I went back to the Airport Utility, and saw that the Extreme was in Bridge Mode. I first tried to switch it to DHCP, and I was thrown an error. I then tried to switch it to DHCP & NAT, and I was able to update. After updating I got the message that something else was already using NAT, and that would create a double instance. So here's my first (and only, for now) question: does this mean that the provider's hardware is providing NAT? Does this mean that that hardware IS doing some routing, and should I push back on them? Or is this something that is expected out of this configuration and can be safely ignored?

Thanks for any help you can offer!
 

Weaselboy

Moderator
Staff member
Jan 23, 2005
30,894
10,666
California
Does this mean that that hardware IS doing some routing, and should I push back on them?
Yes... the double NAT message sounds like there is a router/wifi setup in the providers modem, and you using the AE in bridge mode solves that. You need to get them to put their router in bridge mode so you can use the AE with for NAT and DHCP.
 
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lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
Yes... the double NAT message sounds like there is a router/wifi setup in the providers modem, and you using the AE in bridge mode solves that. You need to get them to put their router in bridge mode so you can use the AE with for NAT and DHCP.
Aha, that's what I thought was going on. Thank you!
 
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lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
Well, not quite there yet it seems. Spoke with my provider, and he looked into the device settings. He says the device is in a "hybrid" bridge mode. It identifies itself as 192.168.5.1, and passes along 192.168.5.50 to the Airport Extreme...and the rest is supposedly up to the Airport Extreme. I can see the 5.1 number, which the Airport Utility identifies as the location of the ROUTER. If he is correct, then their router (which he says is just routing everything to 129.158.5.50 and then hands-off) is only identifying the Airport Extreme. If this is the case, if I put the AE into DHCP & NAT and get the response that there are two NAT instances and I can choose to ignore that...then I should be able to safely ignore that, is that correct? Just go about my regular business knowing that 192.168.5.1 (their device) and 192.168.5.50 (the AE) are all I need to worry about?
 
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BrianBaughn

macrumors 604
Feb 13, 2011
7,073
1,186
Baltimore, Maryland
Providers are changing their equipment and systems in an ongoing process so it's hard to know what your specific solution will be. If you let us know which provider, the level of service (ie home or business) and the model number(s) of the equipment they've installed at your home and also which Airport Extreme you have then someone here with a bit more experience can probably quickly research what's going on.
 
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lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
Hm. As noted, I lack the background to make such judgments, but should I be hesitant to give out that kind of specific information? I'm assuming that there are those that could single me out in some fashion and use such information to determine an attack vector. Does this tinfoil hat make my butt look big?
 
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556fmjoe

macrumors 68020
Apr 19, 2014
2,084
2,050
Hm. As noted, I lack the background to make such judgments, but should I be hesitant to give out that kind of specific information? I'm assuming that there are those that could single me out in some fashion and use such information to determine an attack vector. Does this tinfoil hat make my butt look big?

There's nothing to worry about with giving out that info. Most of it already leaks to every website you visit anyway.
 
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lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
Unless you're the only guy signed up to Frank's Internet Service in Coldville, Alaska…I wouldn't be too concerned with the details I specified.
Thanks for the laugh, that was good!
There's nothing to worry about with giving out that info. Most of it already leaks to every website you visit anyway.
Roger that to you both. I'll collect the info.
 
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lkalliance

macrumors 6502
Original poster
Jul 17, 2015
482
489
@All: It's been a while since I attended this thread, and I wanted to post an update: the issue has been fixed.

The provider had claimed that the modem, operating in "hybrid bridge mode" was not doing any routing...and then explained what routing it was doing :rolleyes:. It had been assigning itself a local IP address and passing along a range of IP addresses my Airport Extreme could use.

Well, the modem was about ten years old, and in the process of going over things the provider suggested, tangentially, that I would get better performance anyway with their current modem. Well, sure. The technician contacts me to arrange the switchout...and tells me he can see my router is in Bridge Mode and it shouldn't be (that's what I've been saying!), and he can tell that the old modem was handling all the routing (THAT'S WHAT I'VE BEEN SAYING!!). Anyway, the new modem works with their new standard IT setup, which does in fact hand the routing over to the Airport Extreme, like it should have been doing (and they claimed it had been doing) all along. I'm no longer in Bridge Mode, there is no Double NAT warning, I have complete control of the local routing. Problem solved.
 
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satcomer

macrumors 604
Feb 19, 2008
7,068
1,202
The Finger Lakes Region
Man you kids seem not to understand ALL Networking revolves Public IPS and you NAT(Network Address Translation) to Private IPs in the 192.168.0.0 Network and the 10.0.0.0 Network, you read about here at Wiki for Private IPs!

Also the general rule in Home Networks on NAT per Home! So in the Home you have the Main Router Closet to the modem doing NAT. So any other NAT router after that Main NAT Router need to have NAT Turned Off!
 
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