Comment 1 for bug 1856852

MicroStack services are generally configurable via files in the .d directories in $SNAP_COMMON/etc/, which is writable.

This means that, if you create a file called opendaylight.conf in /var/snap/microstack/common/etc/neutron/neutron.conf.d/ with your config, then restart the snap, MicroStack's Neutron services should pick up and use your configuration.

Note that, while all the files in /var/snap/microstack/common/etc/neutron.conf.d/ are writable, the existing files are managed by the snap, and changes to them will get overwritten on snap restart. You want to put your custom configuration in a uniquely named .conf file in that directory.