Monday, June 18, 2018

Investigating Docker connectivity issue

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I am trying to reach host-x.com from docker container running on MacOS but it fails:

$ docker run ubuntu:latest \     /bin/bash -c \    'apt-get update &&      apt-get -y install netcat &&      nc -v -z -w 3 host-x.com 443  &> /dev/null && echo "Online" || echo "Offline"'  Offline 

It works fine when:

  • I run a docker container in another machine:

    Online 
  • I run it on my Mac, outside of a docker container:

     nc -v -z -w 3 host-x.com 443  &> /dev/null && echo "Online" || echo "Offline"'        Online 
  • I run it on my Mac from docker container, for other target hosts:

    $ docker run ubuntu:latest \     /bin/bash -c \    'apt-get update &&     apt-get -y install netcat &&     nc -v -z -w 3 www.google.com 443  &> /dev/null && echo "Online" || echo "Offline"'     Online 

UPDATE #1

  1. As suggested I logged in into container and checked DNS. Host name is correctly resolved:

    root@55add56ecc11:/# ping host-x.com PING s1-host-x.com (172.22.187.101) 56(84) bytes of data. 
  2. However, ping packages are not delivered. I though this could be caused by the conflict of IP range in internal docker network and corporate network (172.17.X.X). I tried to fix the docker bridge IP address in my daemon configuration and re-check the connectivity but it didn't help:

    "bip" : "10.10.10.1/8" 
  3. I checked with 3 other persons in my company (4 in total including me). 50% has access to this host (Online), 50% doesn't (Offline).

  4. I tried what @mko suggested, using netcat in interactive mode inside the container. Still timeout.

     root@37c61acc5aa5:/# nc -v -z -w 3 host-x.com 443  s1-host-x.com [172.22.187.101] 443 (?) : Connection timed out   
  5. I tried tracing the route but no success:

    traceroute -m 10 -w 1 host-x.com traceroute to host-x.com (172.22.187.101), 10 hops max, 60 byte packets  1  10.10.10.1 (10.10.10.1)  0.444 ms  0.388 ms  0.364 ms  2  * * *  3  * * *  4  * * *  5  * * *  6  * * *  7  * * *  8  * * *  9  * * * 10  * * * 

How can I investigate that?

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