ubuntu 21 vagrant file is not changing the IP address with reload, how to fix that?

My vagrant file:

# -*- mode: ruby -*-
# vi: set ft=ruby :

# All Vagrant configuration is done below. The "2" in Vagrant.configure
# configures the configuration version (we support older styles for
# backwards compatibility). Please don't change it unless you know what
# you're doing.
Vagrant.configure("2") do |config|

  config.vm.box = "bento/ubuntu-21.04"

  config.vm.define "m11" do |m11|
     m11.vm.hostname  = "firstserver1"
     m11.vm.network "private_network", ip: "150.129.148.251"
     m11.vm.provider "virtualbox" do |vb|
       vb.name = "firstserver1"
     end
  end
  config.vm.define "m21" do |m21|
     m21.vm.hostname  = "secondserver1"
     m21.vm.network "private_network", ip: "150.129.148.252"
     m21.vm.provider "virtualbox" do |vb|
       vb.name = "secondserver1"
     end
  end
  config.vm.define "m31" do |m31|
     m31.vm.hostname  = "thirdserver1"
     m31.vm.network "private_network", ip: "150.129.148.253"
     m31.vm.provider "virtualbox" do |vb|
       vb.name = "thirdserver1"
     end
  end
 config.vm.provision "shell" , path:"docker.sh"
end

When I try to vagrant up, initially by mistake I gave same IP to all the three machines. Later I changed it. I did then vagrant and vagrant reload.But the IP address is not changing.

vagrant halt
vagrant reload

Any suggestions please on how to fix this?

The /etc/network/interfaces is just an empty file here on the OS installed.