Gateway not connecting to internet from a single device

Question

My goal is to try and setup OSMC on a Raspberry Pi v1 Model B that I can use as a media center connected to my living room TV. I have successfully got it hooked up to the TV and the Comcast router/gateway, and the software appears to be running and configured itself appropriately. I preloaded the OS image onto the SD card for the Pi from the most recent .img download of OSMC for Raspberry Pi (Debian based?)(12/28/2015).

The issue is that I have a good LAN connection and am able to SSH into the Pi and ping all LAN resources and the Gateway. Running ifconfig shows that I am leased an IP address from the gateway DHCP service, correct subnet mask and bcast. TX and RX shows no errors or lost packets. Again, all LAN traffic is splendid.

When I SSH into the Pi any ping to an external internet address results in 100% loss. Interestingly enough, DNS names are not resolving correctly either.

The gateway router device is a Comcast Xfinity provided Cisco device model DPC3939. It is showing that the device is connected. All other devices on the network are connecting to internet resources. All LAN to WAN is set to Allow All.

Now here is where things might get tricky. On my home network I am using an old Linksys router with a special open source firmware installed so that it can be used as a wireless bridge to the top floor of my house. This has worked just fine for me for a while now. It reserves 10.0.0.100 LAN IP for itself and the Cisco device seems to recognize it as a bridge. All devices hard connected to the Linksys show up in the XFinity console as Ethernet connected devices. Where I think the router is all messed up is that this Pi used to be running a different SD card with different services connected upstairs to the Linksys. I had to move it downstairs to plug directly into the Cisco router now so it is given a different IP address.

Restarting the Cisco router does not seem to help.

Any help or suggestions for different diagnostics that I can run or things to check to figure out why DHCP and LAN traffic is okay but internet is not working for this single device?

Answer 1

I figured out what the problem was. The problem was rather simple. My Cisco router was blocking the MAC address of my Pi for all LAN to WAN traffic.

How this happened is basically I made a mistake which I am choosing to blame on the reprehensibly bad user interface that Comcast has put on the administration console of this router. It doesn't support devices with a static IP LAN configuration, so if you want a device to have a constant IP address then you need to set a Reserved DHCP IP address. Each entry in this table has a X button next to it that one would naturally think means to remove from the Reserved IP table. No... this X button actually parental control blocks the entire device by MAC address.

I only discovered this after carefully looking at router logs. After removing this from the parental control block the internet worked just fine.