IP Planning - Challenges and Best Practices for Cloud Migration

Generally it is considered always the best approach to migrate to cloud. Of course, there are obvious benefits of capex removal, elasticity and much more but it also come with a number of challenges. IP planning is among the top challenges of cloud adoption if not the top challenge. In this article i want to highlight the challenges of IP planning only and look at some of the best practices to over come these challenge. 

Migrating an enterprise from an on-premise data center to a public cloud requires careful planning and consideration for IP plan. IP plan is usually seen as a plan for network addressing, subnets, and IP ranges allocated across cloud VPC for IaaS and PaaS resources. However it is much more than that. IP planning also contains the IP management and takes care of bigger perspective of cloud framework such as scalability, availability, resiliency as well as multi cloud adoption strategy.

Lets start with the major and well know challenges.

IP Addressing Conflicts: One of the biggest challenges during cloud migration is IP address conflicts. Cloud resources such as virtual machines, load balancers, and databases may have the same IP addresses as on-premise resources, leading to IP address conflicts. 

IP Address Management: With the migration to the cloud, there is a need for effective IP address management. IP addresses must be assigned by a single authority to all cloud resources, managed and tracked under one organization to avoid duplication and any routing issues.

IP Address Range Allocation: In an organization, generally IP address ranges are allocated to various departments or teams. With cloud migration, these IP address ranges may overlap, leading to IP conflicts. 

Now lets see a few challenges which are usually overseen in a poor IP plan.

Route Aggregation issues: Besides the overlapping issue, the IP ranges assigned to one department may run out as that department grows. This issue will lead to a irregular IP segment assignments and route aggregation becomes difficult if not become problematic.

Scaling and Elasticity: As cloud environments are scalable and elastic, there is a need for flexible IP allocation that can cater to scaling needs. IP segments are needed to be whitelisted on the firewall. As more infrastructure resources are created automatically by auto scaling policies, they must belong to the same IP segment which is already whitelisted on the firewall otherwise the network communication from the newly created servers will be disturbed.

Human Readability: It is the job of an IP planner to plan the IP segments in a way that its intuitive and readable by frequent network administrators. With multiple cloud resources, there is a need for proper IP segmentation for better readability of IPs. For example, an IP segment 192.168.0.0/16 is dedicated to development environments under an organization. any IP under this segment such as 192.1681.205 can be quickly understood as development traffic originator or receiver. It makes troubleshooting easier.

Best Practices:

1. Pre-Migration Assessment: Make it a general rule of thumb and conduct a pre-migration assessment of existing IP address allocation. This will not only give you a preliminary idea of number of IPs and IP segments required but also helps you identify potential IP conflicts. Your IP plan should always be based on this assessment. 
2. Dedicated IP Address Range: If there is no limitation seen during the assessment phase, dedicate a new IP address range for cloud resources. This range should be separate from on-premise IP ranges. In this way, you are avoiding the IP conflicts.
3. IP Address Management Tool: Use an IP address management tool to manage and track IP addresses across the whole organization, including cloud resources. Note that the IP resource management must be unified across the whole organization. Usually the organization's network department is responsible for the IP planning and IP segment allocation. However as organization grows and or merge with other organizations, it becomes increasingly complex, hence the need for a unified IP planner arise.
4. IP Address Ranges: The IP address segments should be planned in a flexible manner to accommodate the future needs of excess IPs. It is usually done by using private IP segments such as 10.0.0.0/8 or 172.16.0.0/16 segments and use NAT for communication as the number of available IPs is abundant. It provides extra buffer for new IP requirements in the same IP segment. 
5. Automatic IP Address assignment: In all cloud environments offered today, the option to assign IPs automatically is available as it is also crucial for the automatic scaling of infrastructure resources. it is advised to take advantage of this function in cloud together with an intuitive IP management tool to offload manual efforts.
6. IP Address Audits: The job of a network administrator also necessitates to regularity audit the allocated IP addresses and find any conflicts and overlaps. 

In short,

IP planning is very critical part of cloud migration. It ensures effective communication between cloud resources and on premise without any conflicts. The IP planner should follow the best practices as we discussed above such as IP assessments, dedicated IP address ranges assignment to new infrastructure, intuitive and readable IP planning and performing IP address audits. 

IP planner must work towards standardizing IP addressing schemes, proper use of NAT, adopting new IP address management tools and capabilities of cloud provider such as automatic IP assignment in his IP plan to maximize the effectiveness of the IP infrastructure.