New LEDE user here. As far as I'm aware, I successfully flashed the proper factory bin file to replace the stock firmware. However, I am confused as to what configuration (or lack thereof) is preventing internet access. A user on a different forum gave the impression that a wired connection should be possible without further configuration. The lights on the C5 and the cable modem seem correct, but so far I can only access the C5 via LAN ports for configuration. What might I be overlooking?
You may need to reboot your modem, possibly several times to get it to recognize the router. Particularly if it is a cable modem (at least in the US, many cable internet companies bind to the MAC address of the router or device connected directly to the modem and require a restart to start working with a new (or differently configured) device.
Correlated with the above, you should check to see if the router is getting an IP address on the WAN port. You can check this with the web interface (LuCI) by going to Network > Interfaces and looking at the WAN interface for an IP. Or you can ssh into the system and type "ifconfig" which will show the current status of the interfaces.
Failing that, you will need to post information about your configuration for anyone to be able to help you further. Details such as how things are physically connected are also useful, but most importantly will be the configuration files. You can ssh into the router and then list the contents of specific files. Most of the time, the issue lies in one or more of the following files:
ssh into the device and then use 'cat' to show the file -- copy and paste those files here. for example:
Check the main status page to see what IP you received from the cable modem. If it is in routing instead of bridge mode, it may also be using the 192.168.1.X subnet. This will not let you reach the Internet. You would need to change the router's LAN IP to be in a different subnet, such as 192.168.2.1.
Cable modem decided to die, so replacement is finally in place. Looks like I have not been seeing an IP address for the WAN port compared to the 192.168.1.x on the LAN port under main status. In reviewing documentation, I think I am unclear on what configurations change between the modes. The C5 pings out fine from the diagnostics/utilities section of LEDE when attached downstream from the old router, but not when the C5 is the only router in place. This is with either of the suggested LAN IPs.
Assuming you have everything configured properly (or even just by the defaults), this sounds like what I had described earlier with respect to the need to reboot the modem, possibly many times to get it to bind to the MAC address of your C5 (or talk to your ISP and ask them to release the binding to your old router).
If you have made any changes to the configuration of the LEDE C5, you might want to go back to defaults since that will provide a working baseline solution in many cases.
Aside from that, if you have made changes that you want to keep in place, we will still need to see more info about your configurations in order to help you.
Looks like the MAC address sorted out by restarting the devices in different sequences. Now, to get the Google Cloud Printer working like on the previous router.