[Server] Error Creating Ephemeral Network Bridge

If you are getting the error message related to "ephemeral network bridge" and your docker version is 18.06 and above, create a file /etc/docker/daemon.json on nomad client machines with the below content.


  "default-address-pools": [
    {"base": "", "size": 24}


Note: As a quick fix, you can also terminate nomad-clients. Nomad ASG will automatically spin new nomad clients as per its policy.


Example error message:


Build-agent version 1.219.48216-fe3742fa (2020-12-09T13:47:53+0000)
Docker Engine Version: 18.09.9
Kernel Version: Linux 7cfa8725cxxx 4.4.0-1087-aws #98-Ubuntu SMP Wed Jun 26 05:50:53 UTC 2019 x86_64 Linux

Unexpected environment preparation error: error creating ephemeral network bridge: error creating ephemeral docker network: Error response from daemon: could not find an available, \
non-overlapping IPv4 address pool among the defaults to assign to the network


In case issue is still not resolved, please submit a ticket to Support or write to support@circleci.com along with a Support bundle.

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