Comment 0 for bug 1584092

Fan allows for variable sized subnet map sizes. For example, if I want to map a /24 to a /16 instead of the default /16 to /8, Fan supports this. However, when configuring this via fanatic, I see that docker configuration fails. In /etc/default/docker, the --fixed-cidr flag is defined incorrectly.

$ sudo fanatic
Welcome to the fanatic fan networking wizard. This will help you set
up an example fan network and optionally configure docker and/or LXD touse this network. See fanatic(1) for more details.

Configure fan underlay (hit return to accept, or specify alternative) [192.168.0.0/16]: 192.168.1.0/24
Configure fan overlay (hit return to accept, or specify alternative) [250.0.0.0/8]: 250.99.0.0/16
Create LXD networking for underlay:192.168.1.0/24 overlay:250.99.0.0/16 [Yn]: Y
Profile fan-250-99 created
Create docker networking for underlay:192.168.1.0/24 overlay:250.99.0.0/16 [Yn]: Y
Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.
Test LXD networking for underlay:192.168.1.10/24 overlay:250.99.0.0/16
(NOTE: potentially triggers large image downloads) [Yn]: n
Test docker networking for underlay:192.168.1.10/24 overlay:250.99.0.0/16
(NOTE: potentially triggers large image downloads) [Yn]: n
This host IP address: 192.168.1.10
Remote test host IP address (none to skip):
/usr/sbin/fanatic: Testing skipped

$ grep "DOCKER_OPTS" /etc/default/docker
# Use DOCKER_OPTS to modify the daemon startup options.
#DOCKER_OPTS="--dns 8.8.8.8 --dns 8.8.4.4"
DOCKER_OPTS=" -b fan-250-99 --mtu=1450 --iptables=false --fixed-cidr=250.99.10.0/40"

May 20 05:15:30 macbook docker[27364]: time="2016-05-20T05:15:30.411933688-07:00" level=fatal msg="Error starting daemon: Error initializing network controller: invalid CIDR address: 250.99.10.0/40"