I greatly appreciate your help to show me what is going on with my network.
The situation is like this: I have a LiDAR sensor that streams UDP data over ethernet cable. The LiDAR has a DHCP server running on its board. I need to install dnsmasq so that the LiDAR can directly connect to a NUC (I just followed the manual). Everything works fine. Now I need to use my laptop to ssh the NUC when collecting data. Both my laptop and the NUC connect to a 4G router via wifi. Please have a look at the picture.
Here is the picture.
Without connecting the LiDAR ethernet cable to the NUC, I can ssh from my laptop to the NUC and everything works fine.
However, if I connect the ethernet cable to the NUC to get the LiDAR data, I can't ssh the NUC anymore.
From my laptop:
ifconfig
wlp3s0 Link encap:Ethernet HWaddr 34:f3:9a:fe:bc:fd
inet addr:192.168.1.57 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: 2a02:2121:2cf:cb55:ec0:c6f0:be03:abe0/64 Scope:Global
inet6 addr: fe80::65d3:f133:761d:874f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:39366 errors:0 dropped:0 overruns:0 frame:0
TX packets:28429 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26621126 (26.6 MB) TX bytes:6555066 (6.5 MB)
ip route show
default via 192.168.1.1 dev wlp3s0 proto static metric 600
169.254.0.0/16 dev wlp3s0 scope link metric 1000
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
192.168.1.0/24 dev wlp3s0 proto kernel scope link src 192.168.1.57 metric 600
From the NUC,
ifconfig
wlp58s0 Link encap:Ethernet HWaddr f8:63:3f:5c:55:5d
inet addr:192.168.1.51 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: 2a02:2121:284:9781:d43c:1456:9f1c:fa41/64 Scope:Global
inet6 addr: 2a02:2121:284:9781:f9ac:1884:54fe:af15/64 Scope:Global
inet6 addr: fe80::310b:eb87:967e:cc63/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:394 errors:0 dropped:0 overruns:0 frame:0
TX packets:296 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:65555 (65.5 KB) TX bytes:52734 (52.7 KB)
ip route show
default via 192.168.1.1 dev wlp58s0 proto static metric 600
169.254.0.0/16 dev wlp58s0 scope link metric 1000
192.168.1.0/24 dev wlp58s0 proto kernel scope link src 192.168.1.51 metric 600
On the NUC, after connecting the LiDAR ethernet cable, I can not ping local IPs (gateway192.168.1.1 or my laptop), but I can ping 8.8.8.8.
My guess is that I have to change some settings of dnsmasq but I have no idea what to change.
Thanks for your help!
Edit 1 The suggested solution doesn't work for me. On the NUC I can use both wifi and LAN without problem. I can not use my laptop, which is connected to the same Wifi network, to SSH the NUC (the NUC is connected to the LiDAR via an ethernet cable). Note that, without plugging in the LiDAR's ethernet cable, I can SSH the NUC.
