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I have a remote that I can ping from my macbook's terminal. But when I start my VirtualBox Ubuntu 16.04 VM and ping the same remote host, its not pingable and I get an error saying "Destination Host Unreachable".

Also, I am on my company's VPN when I do this and the remote host is on that network.

I have been trying to look for similar issues online but haven't found anything. How can I debug this? Please let me know any information you need.

Output from my VM:

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.2.2        0.0.0.0         UG        0 0          0 eth0
0.0.0.0         10.0.0.1        0.0.0.0         UG        0 0          0 enp0s8
10.0.0.0        0.0.0.0         255.255.255.0   U         0 0          0 enp0s8
10.0.2.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
172.17.0.0      0.0.0.0         255.255.0.0     U         0 0          0 docker0
172.18.0.0      0.0.0.0         255.255.0.0     U         0 0          0 br-3703e922f98f

$ nslookup eventquery01.mp.local
Server:     172.16.254.11
Address:    172.16.254.11#53

eventquery01.mp.local   canonical name = mpeventquery01.mp.local.
Name:   mpeventquery01.mp.local
Address: 172.18.83.85

$ ping 172.16.254.11
PING 172.16.254.11 (172.16.254.11) 56(84) bytes of data.
64 bytes from 172.16.254.11: icmp_seq=1 ttl=63 time=74.8 ms
64 bytes from 172.16.254.11: icmp_seq=2 ttl=63 time=76.4 ms
64 bytes from 172.16.254.11: icmp_seq=3 ttl=63 time=78.4 ms

$ ping 172.18.83.85
PING 172.18.83.85 (172.18.83.85) 56(84) bytes of data.
From 172.18.0.1 icmp_seq=1 Destination Host Unreachable
From 172.18.0.1 icmp_seq=2 Destination Host Unreachable
From 172.18.0.1 icmp_seq=3 Destination Host Unreachable
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1

According to your routes, all traffic for 172.18.0.0/255.255.0.0, which the IP address 172.18.83.85 is a part of, is being sent to the br-3703e922f98f interface.

If the br-3703e922f98f interface is not on the same network as your remote host eventquery01.mp.local, and they are in fact two separate networks overlapping part of the same subnet, the only way to fix it is to change the network subnet of one of the endpoints to a different network that is not in use.

Is the br-3703e922f98f interface part of a Docker network? If so, there are configuration options to modify the networks that Docker creates, or you can create them manually.

| improve this answer | |
  • Thank you for replying. How can I simply remove that interface? I am not sure who created br-3703e922f98f. – Arjun Jun 29 '18 at 22:58
  • Was it Docker that created the interface? is it still there if the Docker service is stopped? – GracefulRestart Jun 29 '18 at 23:04
  • Yes, you are right! Although stopping docker didn't remove these interfaces. I removed the interfaces docker0 and br-3703e922f98f using ip link del docker0 and now I can ping that host!! Thanks a lot! – Arjun Jun 29 '18 at 23:29
  • To permanently remove it, I had to run: docker network ls docker network rm ... – Arjun Jun 29 '18 at 23:34

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