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cwazytech

macrumors 6502
Original poster
Jan 7, 2009
382
86
Colorado
For one week now I have been successfully connected to the Internet using my Time Capsule + my Xfinity supplied modem/router. When it was hooked up, I told the service guy that I didn't want to use the router function on the supplied modem; that I wanted to use my Time Capsule instead. He told me that I could do this if I put the xfinity router in Bridge mode. Done and done. After one week of flawless service, all of a sudden I lost Internet. The Airport utility suggested that my internet connection was lost and my time capsule was fine. I called xfinity, multiple times, and after many setting changes and restoring the Time Capsule to factory settings it looks like the only way I can get Internet through my time capsule is to leave bridge mode "off" on the xfinity supplied modem/router. Now I'm stuck with a "Double NAT" error that I'm forced to ignore until I can find a better solution. Thoughts?
 

DJLC

macrumors 6502a
Jul 17, 2005
959
404
North Carolina
I'd look at swapping the unit they provided for a standard cable modem. Often you can either request that from the cable provider or, if you're so inclined, buy your own.

I have had many issues in the past using a router with a modem/router combo provided by an ISP. Swapping their unit with a regular old modem usually solves all issues.

Or, as @LiveM said, give up and put the TC in bridge mode, allowing the Xfinity box to handle the routing.
 

monokakata

macrumors 68020
May 8, 2008
2,063
605
Ithaca, NY
This isn't a "just use Google" response, but I wondering whether you searched for similar cases? I say this because a few years ago I was trying to set a friend's modem/router combo (Arris, I think) into bridge mode. I did succeed but not without plenty of Googling. What appeared to be straightforward instructions didn't work. Eventually I found what I was looking for on some message board, rather than on any manufacturer's site, or the cable company's site.

I remember being surprised at just how many sites and forums devoted to cable modems and routers were out there. I don't remember any of them, unfortunately. But they are out there.

If you haven't done this and decide to give it a try, be sure to tack on the modem/router's model number.
 

adam9c1

macrumors 68000
May 2, 2012
1,889
314
Chicagoland
What is probably happening is Crapcast is pushing out a firmware update and it resets their modem/router to default config.
Honestly I'm not sure if there is a way to use their device in bridge mode. You can use your TC in bridge mode however.
 

cwazytech

macrumors 6502
Original poster
Jan 7, 2009
382
86
Colorado
What is probably happening is Crapcast is pushing out a firmware update and it resets their modem/router to default config.
Honestly I'm not sure if there is a way to use their device in bridge mode. You can use your TC in bridge mode however.

This has been the most common response. I can do it, but I was also looking to purchase my own Xfinity compatible modem so that I could return theirs. That would save me $10/month. Maybe I'll just suck it up.
 

adam9c1

macrumors 68000
May 2, 2012
1,889
314
Chicagoland
Yes, you can buy your own modem. Ask your support what's available in your area.
Make sure you keep a good receipt as I've heard stores years later Crapcast says you are still renting or they did not charge you for rental and now they want $.

If you have telephone service with them you have limited options.
 

campyguy

macrumors 68040
Mar 21, 2014
3,413
957
Here's my fix, one that stuck after I figured out what was going on. It's not just a Comcast thing, or an Apple AE/TC thing - I've got offices on a few different ISPs, plus Comcast residential and business accounts. Once I figured it out - using Console and Little Snitch - it was a stupid simple fix, especially when I found that all of my CL fiber or all of my Comcast cable connections were pretty much crapping out at about the same time. If you followed the instructions, like I did, it just works - until it doesn't...

Comcast pings their modems for lots of reasons, with firmware updates being the least likely reason - lease renewals are more likely. What happens at these lease renewals is a soft reboot of the modem - which includes temporarily reactivating the DHCP server built into the router and temporarily reactivating NAT, and you know the rest. Double NAT, and a need for a double expresso or a double Irish Whiskey...

Almost all of my cable modems ship with a default 192.168.xxx.xxx address (the one I'm on now - a Netgear CM500 uses 192.168.100.1 but the Motorola SB6141 I used before that uses 192.168.1.1 and IMO there's issues with this "older" but still common address, read on). Following the installation instructions for your AE/TC relative to any of Comcast's modems (all of mine are purchased from a reseller, even for my BCI accounts - this does not matter here) generally yields a iPv4 DHCP Range of 192.168.1.2 to 192.168.1.200.

With my SB6141 and a couple of the BCI-issued modems were trying to temporarily assign the same DHCP Range of 192.168.1.2 to 192.168.1.200 during this lease renewal that the AE/TC is trying to assign to your network, and there's your Double NAT issue...

There's two fixes, on in software and the other in hardware. The hardware fix is simple - buy a modem that uses a different IP address, like the newer Arris SB6183 or CM500 - both use the same Broadcom chipset and 192.168.100.1 address.

Before I ponied up for a few new modems, the software fix is to change in Airport Utility from the iPv4 DHCP Range of 192.168.1.2 to 192.168.1.200 to one of the two different options - after switching (in the Utility's Network>Network Options... settings) to a Range of 10.0.1.2 to 10.0.1.200 I have had zero issues between my modems and AE/TC devices and other routers, and zero down time. Once a week, my modems phone home, eventually sync and get a new lease, and I never notice a thing...

Get your AE/TC/router DHCP Range assignment as far away as you can from the router's default IP range - or just on a different range of numbers. I hope this helps. If it does, mail a couple of fingers of Irish Whiskey to me - you won't need it!
 
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