Undocumented network 172.18.0.0/16 in some ONAP VMs - can it be re-configured

 
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While installing ONAP on a vanilla Openstack (Ocata), we used 172.18.1.0/24 as the network for controller/Compute node and the provider network. Later we found that vm1-dcae-controller vm1-message-router,  vm1-appc, vm1-sdnc and vm1-policy have routing entries like this:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.0.1        0.0.0.0         UG    0      0        0 eth0
10.0.0.0        *               255.0.0.0       U     0      0        0 eth0
169.254.169.254 10.0.0.1        255.255.255.255 UGH   0      0        0 eth0
172.17.0.0      *               255.255.0.0     U     0      0        0 docker0
172.18.0.0      *               255.255.0.0     U     0      0        0 br-99c842c00ca6


Is there a way to reconfigure the network to something else or even change the netmask to 255.255.255.0 before VM and/or the container start to use the 17.18.1.0 network?

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    1 answer

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      those are the choices made by docker engine running on those VMs.  you could add command line options (--bip and --fixed-cidr) to the docker start command to change those choices.  

      1. Josef Reisinger

        Hi Lusheng, thanks for your response.

        I am not a docker expert, but I so far assumed the 172.17.0.0/16 is choose by docker and applies to the docker0 bridge (which can be changed by --bip) . 172.18.0.0/16 seems to be created by the container and uses a different bridge 'br-99c842c00ca6'. Can you confirm that 172.18.0.0/16 is created by the docker daemon?

      2. Lusheng Ji

        Josef,

        Sorry for the late response.  Been busy at the ONAP dev conf.

        You are correct, the 172.17/16 network is indeed picked by the dockerd.  The 172.18/16 network is created by docker-compose by default.  So on VMs that docker-compose is used for spinning up multiple containers you will see this kind of two-bridge arrangement.

        Now to change the 172.17/16 network address space, created by dockerd, you will need to add the option --bip.  For changing 172.18/16 network address, it is a bit trickier.  You would need to add a network def block with preferred address space definition inside of the docker-compose.yml file; then inside of each service def block add a network subblock referencing this network you just defined.  

        The docker-compose.yml file can usually be found under /opt.

        Lusheng

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