After upgrade to 18.06.5 router fails to connect to WAN

[Passiday]

I know this sounds like a trivial problem but I have exhausted the troubleshooting menu.

After firmware upgrade from 15.05.1 to 18.06.5, the router booted up, launched the WiFi access points and I can connect to the router using the previous wifi access credentials, and I receive correct IP address via DHCP. I can connect to the LuCI, log in and it appears that the configuration has been successfully migrated. But the one thing not working is that there is no connection to the internet.

My gateway to the internet is 4G router. It's configuration capabilities are pretty simple and there is no way to set up DHCP so that specific IP address is assigned to client with specific MAC. So I have disabled the DHCP interface and use static IPs when connecting to the Internet directly through the 4G router. The gateway router's address is 192.168.2.1, and the OpenWrt router's WAN interface is assigned 192.168.2.2 address. There is a wired connection from the 4G router to the OpenWrt router. I have verified if I can connect to the Internet with my PC directly through the 4G router, using ethernet wire and static IP 192.168.2.2, and the connection works flawlessly. However, if the very same wire is then plugged in the OpenWrt router's "Internet" port, the WAN connection is not esablished, no matter how many times one or other or both routers are restarted.

Here's how my Interfaces in LuCI look like:

And here's the WAN interface config:

Here's ifconfig command output:

br-lan    Link encap:Ethernet  HWaddr 14:XX:XX:XX:XX:XX  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: xxxx::xxxx:xxxx:xxxx:xxce/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:15539 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11594 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1462843 (1.3 MiB)  TX bytes:2595692 (2.4 MiB)

eth0      Link encap:Ethernet  HWaddr 16:XX:XX:XX:XX:XX  
          inet addr:192.168.2.2  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: xxxx::xxxx:xxxx:xxxx:xxce/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1097 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:532 
          RX bytes:0 (0.0 B)  TX bytes:53145 (51.8 KiB)
          Interrupt:37 

eth1      Link encap:Ethernet  HWaddr 14:XX:XX:XX:XX:XX  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1185 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:532 
          RX bytes:0 (0.0 B)  TX bytes:206581 (201.7 KiB)
          Interrupt:36 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:3097 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3097 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:284109 (277.4 KiB)  TX bytes:284109 (277.4 KiB)

wlan0     Link encap:Ethernet  HWaddr YY:YY:YY:YY:YY:D0  
          inet6 addr: xxxx::xxxx:xxxx:xxxx:xxd0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:694 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1337 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:96940 (94.6 KiB)  TX bytes:264636 (258.4 KiB)

wlan1     Link encap:Ethernet  HWaddr YY:YY:YY:YY:YY:CF  
          inet6 addr: xxxx::xxxx:xxxx:xxxx:xxcf/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:14708 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12645 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1580709 (1.5 MiB)  TX bytes:3020180 (2.8 MiB)

Pinging from the router the WAN gateway address gets stuck (does not show "Destination Host Unreachable"):

# ping 192.168.2.1
PING 192.168.2.1 (192.168.2.1): 56 data bytes
^C
--- 192.168.2.1 ping statistics ---
153 packets transmitted, 0 packets received, 100% packet loss

I'm grateful for any insights how to make the WAN connection great again.

[psherman]

Keeping your settings from such an old version is not recommended. Try resetting to defaults and recreating your settings manually. Before doing this, you can create a backup of the current configuration to use as a reference, but it should not be restored using the automatic function.

[Passiday]

Ok, factory reset and several hours of manual configuration, and this thing is finished. The proposal of sysupgrade command to preserve the configuration led me to expect that there should be no problems with migration. What's more, the configuration seemed to be almost ok, with that one problematic WAN connection thing.

Perhaps that was not the only issue, but if it helps anyone, the configuration carried over from 15.05.1 had eth0 for the WAN network interface name. But now with a clean config I see that in 18.06.5 (and perhaps earlier) this interface is named eth1.2. I guess this might be the reason behind that WAN connection problem.