CGM4331COM - wifi devices not talk to or ping each other

Hey there @Dasummers! Thanks for reaching out via forums. If possible, I'd like to ask a few follow-up questions to get a better understanding of the ask here. What ping are you referring to exactly? Usually a ping is from the device to a website, no necessarily device to device. Are you using the network broadcasting from the Xfinity gateway, or a network from a secondary router?

@ComcastBrie  Actually FWIW,  ping is a very useful tool that is used for troubleshooting WAN, or even quite commonly, inter-LAN connectivity issues.

As EG pointed out, ping is commonly used regardless of LAN / WAN relationship between two devices. But especially on a LAN, since there is usually no firewall between LAN devices or other routing or DNS, a ping between LAN devices should always work, if the correct IP addresses and subnet masks are used. I am simply using it as a tool to establish the devices on the LAN aren't communicating with each other even at a basic level. Everything can talk to the router and out to the WAN, but not amongst themselves. I'm referring to connecting to cameras, accessing media servers, or accessing printers from other devices on the same LAN.

For example, if my router is at 192.168.1.1, and two wifi devices are at 192.168.1.2 and 192.168.1.3, the .2 and .3 devices should be able to ping each other. They cannot.

I am using the network broadcasting from the xfinity gateway, not a secondary router.

This is a repeated issue, with multiple posts on this forum, and no clear solution provided by xfinity. please determine what is so unique about CGM4331COM to prevent wifi printers from being accessible from other devices on the network. I've done everything I can think of (reset printer & re-establish connection to router, re-installed printer, upgraded printer firmware, turned off firewall, tried ping (failed), used separate 2.5 and 5 GHz and both devices are on the same 2.4 GHz, and still the problem persists. Clearly this is an issue with a setting on the router . Please figure it out and broadcast it here!

... search for "Xfinity Support" ...

"Search for Xfinity Support" is not good advice, as the only "search" that appears on the initial peer-to-peer screen won't find "Xfinity Support" unless the user has already sent a message to them or received one from them.

Instead:

• Click "Sign In" if necessary
• Click the "Peer to peer chat" icon or https://forums.xfinity.com/peer-to-peer-chat
• Click the "New message" (pencil and paper) icon
• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line
• Type your message in the text area near the bottom of the window
• Press Enter to send it

See https://forums.xfinity.com/conversations/email/cant-create-a-new-email-address/605e52b726aa974d63032d02?commentId=606107ea738c7f46a02b830e

I tried the private message but got no response. Which modem signals are you looking for? Wifi or WAN? Is this something I could simply retrieve via the logging into the modem?

Thanks for clarifying BruceW!

I have the xb7, there was no special setting i had to set, all my devices communicate just like there supposed to, my printer works great, only time there might be a issue is if the printer or other device is offline for a while, when it comes back online it might get a new ip if the lease expired, as long as i have the correct ip everything works for me also they must be on the same subnet

@ComcastGabe 

FWIW, a WAN RF signal impairment would not have any effect on one's inter-LAN connectivity.

@EG I wouldn't think so either. But we are talking software, so there may be a bug / feature, however unlikely. My previous router had such a feature to firewall the guest wifi network such that those devices could only talk to the WAN, and it was a simple check box to enable. I am wondering if there are firmware differences, since their are plenty of unresolved posts on this forum, yet plenty of others do not have this issue. Is there someone who could point me where to find my firmware so we could compare?

WAN (modem component) RF system signals and the LAN ethernet are two completely different and separate systems.

Are these modems just garbage? Seems to be a lot of posts where people exchanged them for other models. I think may go back to using my own modem, unless comcast can chime in with an actual solution, rather than just a red herring type of question to spin my wheels.

Thanks. Looks like I am stuck with this modem, since I have one of their wireless tv boxes, and it requires this modem. Can we get this issue escalated to someone with a brain? I realize I'm dealing with some of the lowest intelligence from Comcast here, but this sure seems like an extremely common  problem easily fixed with a software revision. How about it? Or should I just ditch comcast altogether?

@dasummers Just out of curiosity, how are these devices getting their ips? Dhcp or are you assigning a static ip? 

@jlavaseur I'm doing a mix of both. Dhcp limited to .10 through .200 range. Static IPs assigned above .200 range.