no internet although DHCP is working

Question

My issue is similar to what is described here: Raspberry Pi has no internet and cannot ping primary router when connected to repeater

I was playing around with PiVPN (WireGuard) and invoked the command pivipn uninstall - after that the result from trying to ping my router (192.168.1.1) is that the first line is PING 192.168.1.1 ... and all subsequent lines list the Pi's own IP address instead of the router's...? All pings are lost.

arp -n

yields HWadress incomplete...

I've tried a bunch of things but I'm stumped.

Can anyone point me in the right direction?

EDIT:

Ingo asked for the output from the following commands:

IP ADDR:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    net 127.0.0.1/8 scope host lo
      valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
      valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP.LOWER_UP> mtu 1500 qdisc mq master br0 state UP group default qlen 1000
    link/ether dc:a6:32:07:55:6f bed ff:ff:ff:ff:ff:ff
    inet 192.168.1.12/24 brd 192.168.1.255 scope global dynamic noprefixroute eth0
       valid_lft 863473sec preferred_lft 755473sec
    inet6 fe80::b5f3::9c5a::7fcc::cdda/64 scope link
      valid_lft forever preferred_lft forever
3: br0: <BROADCAST,MULTICAST> mtu 1500 qdisc state state DOWN group default qlen 1000
4: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether dc:a6:32:07:55:70 brd ff:ff:ff:ff:ff:ff
IP ROUTE:
default via 192.168.1.1 dev eth0 proto dhcp src 192.168.1.12 metric 202
192.168.1.0/24 dev eth0 proto dhcp scope link src 192.168.1.12 metric 202

If I enable these two lines in dhcpcd.conf, the interface br0 gets the address 192.168.1.12 and it kinda works... I'm very confused:

denyinterfaces wlan0 eth0
interface br0

END EDIT

It would be great if this could be resolved - I'm banging my head against the wall... :(

Best regards, Andrew

score 2 · Answer 1 · answered Jan 16 '21 at 21:48

eth0 with master br0 is slave interface of a bridge br0. Slave interfaces never have an ip address but yours have. The bridge itself is down. In addition there is no other interface with master br0. A bridge with only one slave interface (eth0) doesn't make much sense. There is nothing to bridge.

That all together is a complete messed up and unspecified "configuration". Its behavior is completely unpredictable. You should clean up the setup. Either remove the bridge, or set it up correctly with no ip address on eth0 but on br0 and a second slave interface.

score 1 · Accepted Answer · answered Jan 02 '21 at 23:50

Answer:

You may find it easier to re-flash your SD card with a fresh image, and start over.

Other Things to Consider:

1. You shoulda' had a backup:

We have several must-read Q&A here on the subject of backups:

Can a Raspberry Pi be used to create a backup of itself?
How do I backup my Raspberry Pi?
And saving the best (and easiest) for last, here's my favored backup solution

2. Keeping a spare SD card will provide you with additional options when you find yourself in this situation.

For example, if you want/need to recover files from your troublesome SD card, or if you want to do a post-mortem to discover where you went wrong. With a USB adapter-thing-y (as shown below), you can be restored -literally- in a minute or two:

Imagine: If you maintained a backup on this spare SD card, and you ran into this problem, you could do this:

sudo shutdown
swap the spare/backup SD card for the damaged one in your RPi, and
reboot

You could have resolved this problem in far less time than we've taken posting and answering this question!

score 0 · Answer 3 · answered Jan 17 '21 at 12:56

Thank you Ingo for this analysis. I honestly don't know how I got here and wouldn't know how to go about fixing it. I honestly don't understand anything of what you wrote here - that is absolutely due to my knowledge-deficit.

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP group default qlen 1000
    link/ether dc:a6:32:07:55:6f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::dea6:32ff:fe07:556f/64 scope link 
       valid_lft forever preferred_lft forever
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether f2:ea:7e:5b:ba:a4 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.12/24 brd 192.168.1.255 scope global dynamic noprefixroute br0
       valid_lft 843201sec preferred_lft 735201sec
    inet6 2001:4dd5:4075:0:10d:3893:d2:e632/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 7115sec preferred_lft 3515sec
    inet6 fe80::d847:a8aa:3a86:c9d0/64 scope link 
       valid_lft forever preferred_lft forever
4: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether dc:a6:32:07:55:70 brd ff:ff:ff:ff:ff:ff

This is what I'm now working with after fiddling with it some more. It works, but I don't know why...

Thank you again very much for your input. I'm trying to wrap my head around the networking, but I'm obviously having trouble.