I have been having problems with the Pi and networking. It seems Raspbian uses dhcpcd.conf to run the networking. While this is ok for the Pi while it is getting a DHCP address, it is no good for multiple ip addresses on the same interface. I decided to convert it to systemd.
I found this tutorial --> https://raspberrypi.stackexchange.com/questions/78787/howto-migrate-from-networking-to-systemd-networkd-with-dynamic-failover
What I did...Step 1, Step 2, skipped the rest.
I added all the ip addresses to the /etc/systemd/network/04-eth.network
[Match]
Name=e*
[Network]
#to use static ip (with your settings) toggle commenting in the next 8 lines.
Address=192.168.0.13/24
Address=192.168.0.14/24
Address=192.168.0.15/24
DNS=192.168.0.1
[Route]
Gateway=192.168.0.1
Metric=19
#DHCP=yes
#[DHCP]
#RouteMetric=10