When deploying an overcloud with an external load balancer the IPs specified in external-lb.yaml do not get assigned correctly

Issue

• When deploying an overcloud with an external load balancer the IPs specified in external-lb.yaml do not get assigned correctly.
• Some controller nodes get the IP specified in external-lb.yaml, but other controller nodes get IPs in the range that were not specified.
• The command used to deploy the overcloud was:

openstack overcloud deploy --templates ~/templates/my-overcloud  -e /usr/share/openstack-tripleo-heat-templates/environments/external-loadbalancer-vip.yaml  -e ~/templates/external-lb.yaml  -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml  -e /home/stack/templates/network-environment.yaml --control-flavor control --compute-flavor compute  --ntp-server time.example.com --neutron-network-type vxlan --neutron-tunnel-types vxlan --control-scale 3 --compute-scale 1