Re-IP (Re-IPping) in SRM (Site Recovery Manager) refers to the process of changing the IP addresses of recovered virtual machines during a failover. This is necessary when the virtual machines are moved to a different site or network during disaster recovery to ensure they can function correctly in the new environment. Re-IPping can be done manually or automatically using SRM’s IP customization feature. Below, I’ll provide an overview of both methods with examples:

1. Manual Re-IP:Manual Re-IP involves manually changing the IP addresses of virtual machines after they have been recovered at the secondary site. This method is suitable for a small number of VMs and when you have a simple network configuration.Example: Let’s say you have a virtual machine with the following network configuration at the primary site (source):
   • Original IP: 192.168.1.100
   • Subnet Mask: 255.255.255.0
   • Default Gateway: 192.168.1.1
   • DNS Server: 192.168.1.10
   After failover to the secondary site (target), you would manually reconfigure the network settings to match the new environment:
   • New IP: 10.10.10.100
   • Subnet Mask: 255.255.255.0
   • Default Gateway: 10.10.10.1
   • DNS Server: 10.10.10.10
2. Automatic Re-IP with IP Customization:SRM provides an IP customization feature that automatically handles the re-IPping process for virtual machines during failover. It uses guest customization scripts to modify network settings in the guest operating system.Example: In SRM, you can define an IP customization script that specifies the new IP settings for virtual machines during failover. Here’s an example of a simple IP customization script for a Windows VM:

param (
    [string]$vmIpAddress,
    [string]$vmSubnetMask,
    [string]$vmDefaultGateway,
    [string]$vmDnsServer
)

# Set IP Address
netsh interface ipv4 set address "Local Area Connection" static $vmIpAddress $vmSubnetMask $vmDefaultGateway 1

# Set DNS Server
netsh interface ipv4 set dnsserver "Local Area Connection" static $vmDnsServer

1. When the failover is initiated, SRM will execute this script and pass the new IP settings provided by the secondary site to the VM’s operating system.Note: The actual script syntax and commands might vary based on the guest operating system and network configuration. You can create different scripts for different guest OS types.

It’s important to plan and test the Re-IP process before implementing it in a production environment. Properly updating network configurations is critical to avoid connectivity issues and ensure a smooth disaster recovery process. Additionally, consider factors like DNS updates, application reconfiguration, and firewall rules during the Re-IP process to ensure full functionality of the recovered VMs in the new environment.