I have been using the new XB3 modem/router for the last 6 months or so, and there is something inherently wrong with its networking abilities. I am a Network Administrator professionally, so I am not speaking out of ignorance here. There are several issues I have repeatedly seen/documented since I have been using it.
1. If you have additional WAPs (wireless access points) in your house, the router gets confused when you switch between the XB3 WiFi and other WAPs, and vice versa. It's like the internal XB3 switch is unable to update the internal dynamic ARP tables when you move between WiFi and Ethernet connections (as the other WAPs are connected via ethernet). You have to reboot everything (XB3 and WAPs) to get everything to sync back up and work. This happens routinely, like every week or two.
2. The XB3's internal switch/WiFi again seems to have a hard time with networking print jobs to at least WiFi connected printers. If I haven't rebooted the XB3 in a week or two, and then try to print to a WiFi connected printer, it takes several minutes for a very small print job to actually be spooled to the printer. If I then reboot the XB3, the same print job will be spooled and printed within 10-15 seconds. I have confirmed this same issue on another XB3 modem at a friend's house, so I know it doesn't have anything specifically to do with me or my printer. The common thread is the XB3 modem. I have also tried a different (new) printer on my network and the same thing happens.
3. I have setup a couple of port forwards on the XB3 firewall for gaming purposes. The setup works fine for a week or two, but then stops working. When I log into the XB3 web interface to check if the port forwards are still there, I always find that they are missing, nor will it let me re-add them. Through trial and error, I have found that if I reboot the XB3 the port forwards magically show back up on the web interface and start working again. This wouldn't be a big deal if it happened every few months, but it happens every week or two just like the other 2 problems mentioned above.
4. The performance of the XB3 is a bit erratic. This is most noticeable when surfing the web. Sometimes pages load quickly and sometimes they take forever or don't load at all. My family is constantly complaining to me that they can't get pages or videos to load. Rebooting will typically fix it temporarily, but it never holds. I have checked all my connection metrics (signal strength, etc.) and it all appears to be in spec with things I have read in these forums.
If the XB3 problems noted above were limited to me, I would think that I had a hardware issue with my particular modem. As I have seen the same issues on other people's XB3 routers, it would appear that there is something inherently wrong with it, most likely firmware issues. I have tried to talk with Comcast tech support about them, but they just want you to reboot everything and of course everything starts working again so they assume it is all good. Tyring to explain that the problems will come back in a week or two does not seem to be of concern to them.
I am not asking anyone to fix anything here, only airing my frustration with this. More should be done by Comcast (and perhaps Cisco, the router manufacturer) to bolster the quality of this device. It is one of the worst routers I have ever used within consumer level devices. Most $50 brandname routers/modems you can readily buy at a local store perform way better than this thing.
I have since put my XB3 into bridge mode and attached a $60 netgear router to it and amazingly all is working great now. What does that tell you?
If anyone else reads this and is having similar issues with their XB3, you might think about trying bridge mode with a new router attached to the XB3's LAN port 1. Maybe it will save you the six months of frustration I have gone through. Ugh!
"If anyone else reads this and is having similar issues with their XB3, you might think about trying bridge mode with a new router attached to the XB3's LAN port 1." Can you translate into something simpler? I am so fed up. They always want to blame it on my computer or wireless.
I'm having issues with the new "wireless gateway" that Comcast insisted I needed. I'm unable to view my home security cameras from anywhere outside my home, used to be I would just type in the IP : Port# and there was the image, but ever since I installed this "Upgrade" that doesn't work.
Your comment about "Bridge" mode intrigues me, however not being that savvy with networking stuff I'm not sure how to go about changing that.
Downstream of the Comcast equipment I have a Linksys WRT54GL set up for WiFi using an SSID of 'Dog1', also connected to two Cisco switches and a second D-Link unit that is set up for WiFi using an SSID of 'Dog2'.
Can I just change the setting in the Comcast POS to "Bridge", or is there something else I need to do? Any insight you can provide would be greatly appreciated. Thanks!
There was talk of "bridge" mode being put into the firmware of some gateways. Im not sure on when and if it was rolled out. 1 call to Comcast and they can toggle bridge mode and disable the router/DHCP function of the gateway, which Im betting is your issue. Just know, once the gateway is put into bridge mode, only port 1 on the back will be active, so switch your ethernet if need be.
If you have more than 1 device trying to direct traffic (packets) you are bound to have issues. Imagine arriving at an intersection and 2 traffic cops are standing side by side waving their arms. Which one do you listen to? This is what happens when you have 2 routers connected to each other (with DHCP enabled).