Lost network connection but WiFi still working

[backstander]

Pi Model: 3 B
RetroPie Version Used: 4.0.1
Built From: SD Image

I've done all the usual hardware troubleshooting like making sure my ethernet cable works and my router works and I've even power cycled these devices. The ethernet I/O lights blink and light up like normal when I have a ethernet cable plugged in. I had a similar issue a long time ago using RetroPie 3.6 (I believe) when I lost all network (wired and WiFi) after installing Raspbian from the RetroPie-Setup Script but this time I haven't installed Raspbian and I still have working WiFi. How I fixed it last time was to just re-flash my sdcard.

I'm not sure were to start but this is what I've tried!

sudo nano /etc/network/interfaces

I had this:

iface eth0 inet manual

so I changed it to this:

auto eth0
iface eth0 inet dhcp

but this didn't fix the issue and now it take a little longer to boot

Anyone has any ideas?

[BuZz]

The default config is correct for working with DHCP - you don't need to change it.

Please change the config back, reboot with ethernet connected and post the output of these three commands (via pastebin.com or similar)

ping -c5 8.8.8.8
ifconfig
sudo dhclient eth0
ping -c5 8.8.8.8
dmesg

[backstander]

Okay, I reverted the changes make to /etc/network/interfaces and I disconnected to the WiFi network and rebooted.

So this is what I get after running ping -c5 8.8.8.8

connect: Network is unreachable

After running sudo dhclient eth0 and then running ping -c5 8.8.8.8 I get the same as before

connect: Network is unreachable

And here is my output from ifconfig and dmesg
http://pastebin.com/GATS5rsY

[backstander]

Okay, now I feel silly...

I forgot I had a Network Switch between my Raspberry Pi and my router and I power cycled it and reseated all cables and now my Raspberry Pi is working even though my Roku was working before without any problems.

This issue is resolved! Thanks for your help @BuZz and time on this!