LXC containers get dynamic IP from DHCP. When you stop and start a container, its IP gets changed. If you hosting some web application on this container, you need to point the application to new IP. To avoid this, you can configure static IP on the container.
LXC containers get IP in the range 10.0.3.2-255. To make CentOS container IP static, edit file
vi /etc/sysconfig/network-scripts/ifcfg-eth0
Find
BOOTPROTO=dhcp
Replace with
BOOTPROTO=STATIC
Add below
IPADDR=10.0.3.2 GATEWAY=10.0.3.1 DNS1=1.1.1.1 DNS1=8.8.8.8
10.0.3.2 = replace with any unused IP in the range your LXC container assign using DHCP.
Create a static route file
vi /etc/sysconfig/network-scripts/route-eth0
Add
10.0.3.1 dev eth0 default via 10.0.3.1 dev eth0
After restarting the LXC container, you will have a fixed IP.
reboot