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Simon A. Eugster
Asked: 2021-07-30 06:00:01 +0800 CST

Cannot ping device from one laptop

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I have an Art-Net device and two laptops, a Lenovo x270 running Ubuntu 21.04 and a Lenovo T14 running Ubuntu 20.04. To connect to the Art-Net device, I use an Ethernet adapter on the laptop which I connect directly to the device.

The device address is 2.0.0.5 and for the laptop I use 2.0.0.4, so I configure the Ethernet adapter as follows:

sudo ifconfig enxd03745229ac8 2.0.0.4 netmask 255.0.0.0 up
sudo route add -host 2.0.0.5 gw 2.0.0.4 dev enxd03745229ac8

After that, I can ping the Art-Net device from the x270, but not from the T14 laptop.

Why is that? Are there additional places where the package might get routed somewhere else on the T14?

ifconfig/route output

x270

user@user-ThinkPad-X270 ~/m/Artnet (master)> ifconfig enxd03745229ac8
enxd03745229ac8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 2.0.0.4  netmask 255.255.255.0  broadcast 2.0.0.255
        ether d0:37:45:22:9a:c8  txqueuelen 1000  (Ethernet)
        RX packets 1  bytes 46 (46.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 592  bytes 247929 (247.9 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

user@user-ThinkPad-X270 ~/m/Artnet (master)> route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    600    0        0 wlp3s0
2.0.0.0         0.0.0.0         255.255.255.0   U     0      0        0 enxd03745229ac8
2.0.0.5         2.0.0.4         255.255.255.255 UGH   0      0        0 enxd03745229ac8
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 wlp3s0
192.168.1.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp3s0

> ping 2.0.0.5
PING 2.0.0.5 (2.0.0.5) 56(84) bytes of data.
64 bytes from 2.0.0.5: icmp_seq=1 ttl=255 time=1.36 ms
64 bytes from 2.0.0.5: icmp_seq=2 ttl=255 time=3.94 ms
^C
--- 2.0.0.5 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 1.364/2.652/3.940/1.288 ms

T14

simon@simon-t14 /d/w/m/m/Artnet (master)> ifconfig enxd03745229ac8
enxd03745229ac8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 2.0.0.4  netmask 255.0.0.0  broadcast 2.255.255.255
        ether d0:37:45:22:9a:c8  txqueuelen 1000  (Ethernet)
        RX packets 5  bytes 382 (382.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 300  bytes 187644 (187.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

simon@simon-t14 /d/w/m/m/Artnet (master)> route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    600    0        0 wlp3s0
2.0.0.0         0.0.0.0         255.0.0.0       U     0      0        0 enxd03745229ac8
4.0.0.0         0.0.0.0         255.0.0.0       U     0      0        0 enp5s0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 enxd03745229ac8
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
192.168.1.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp3s0
simon@simon-t14 /d/w/m/m/Artnet (master)> ping 2.0.0.5
PING 2.0.0.5 (2.0.0.5) 56(84) bytes of data.
^C
--- 2.0.0.5 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2051ms
networking

1 Answers

  1. Do not use the same IP address for both laptops. It is never good to use the same IP address for different devices. Set the T14's ip address to 2.0.0.6 and that should do it.

    I also avoid using the first 5 addresses at the beginning and end of a subnet to avoid duplicate IP issues with gateways and other network devices.

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