Google Cloud Platform

Inside an Enterprise: A Glimpse into a Production Virtual Private Could Environment

Cloud computing is a technology that allows users to access and use computing resources such as servers, storage, databases, and software over the internet, rather than having to install and maintain them on their own local devices. This model of computing enables users to scale resources up or down based on demand, pay only for what they use (typically on a subscription basis), and access their data and applications from anywhere with an internet connection. Cloud computing is divided into three main service models: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

An organization can leverage Google Cloud Platform (GCP) Virtual Private Cloud (VPC) to create a secure, isolated network environment for their workloads, providing a foundation for their digital infrastructure. Key features of a GCP VPC include:

Scalability: GCP VPC can be easily scaled up or down based on the organization’s needs. This helps in accommodating rapid changes in workload demands and ensuring smooth operations.

Customization: Organizations can customize their VPC by specifying IP address ranges, creating subnetworks, and configuring firewall rules to control traffic.

Security: GCP VPC offers various security features, including private IP addresses, encrypted data transfer, and Identity and Access Management (IAM) controls, ensuring data protection and compliance with industry standards.

Connectivity: VPC networks can be connected to on-premises networks or other cloud providers using Cloud VPN, Cloud Interconnect, or dedicated links, enabling hybrid cloud deployments and multi-cloud strategies.

High Availability: GCP VPC offers multiple redundancy options to ensure high availability, including zonal deployments, regional deployments, and multi-region deployments.

Cost Optimization: Organizations can optimize costs by using GCP VPC’s features like auto-scaling, pay-as-you-go pricing, and flexible pricing models.

Overall, leveraging GCP VPC helps organizations achieve greater agility, security, scalability, and cost-efficiency for their cloud workloads.

AWS Virtual Private Cloud

Amazon Web Services (AWS) is a comprehensive and widely used cloud computing platform provided by Amazon. It offers a vast array of services, including computing power, storage options, databases, machine learning, analytics, and more. AWS allows organizations to leverage scalable and flexible cloud resources, eliminating the need for extensive infrastructure management and upfront capital expenses.

One critical component of AWS is the Virtual Private Cloud (VPC), which enables users to create a logically isolated section of the AWS Cloud where they can launch resources. VPC provides a virtual network environment that closely resembles a traditional network, allowing users to define their own IP address range, create subnets, and configure routing tables. This level of control and customization ensures that users can design and deploy their applications securely within the AWS infrastructure.

Key features of AWS VPC include the ability to connect the VPC to an on-premises data center using a Virtual Private Network (VPN) or AWS Direct Connect, control inbound and outbound traffic using network Access Control Lists (ACLs) and security groups, and launch resources like Amazon EC2 instances (virtual servers) within the VPC.

In summary, AWS is a leading cloud computing platform that provides a wide range of services, and the Virtual Private Cloud (VPC) is a crucial component that allows users to create and customize their isolated network environments within the AWS infrastructure. This flexibility and control make AWS and VPC a popular choice for organizations seeking scalable, secure, and reliable cloud solutions.


F5 BIG-IP Load Balancer is a high-performance application delivery controller (ADC) designed to distribute incoming network traffic across multiple servers or resources to optimize application availability, performance, and scalability. As a load balancer, it ensures that no single server is overwhelmed, improving resource utilization and preventing downtime due to server failures.

BIG-IP Load Balancer uses advanced algorithms to intelligently distribute traffic based on factors like server health, performance, and user session persistence. It can be deployed in various scenarios, such as on-premises data centers, cloud environments, or hybrid infrastructures, making it suitable for diverse application deployment models.

Additionally, the BIG-IP platform offers additional features like SSL offloading, application firewall, traffic shaping, and advanced security capabilities, making it a comprehensive solution for enhancing application delivery, security, and performance. By efficiently managing and distributing traffic, BIG-IP Load Balancer ensures a seamless and optimal user experience for applications while providing high availability and reliability.


DMVPN stands for Dynamic Multipoint Virtual Private Network. It is a network solution that allows for the creation of virtual private networks (VPNs) over the Internet or any IP network. DMVPN is designed to provide a scalable and flexible approach to building secure site-to-site VPNs in a dynamic and cost-effective manner.

Traditional VPN solutions typically require a point-to-point connection between each site in the network. This can become complex and difficult to manage as the number of sites increases. DMVPN addresses this challenge by utilizing a hub-and-spoke architecture with dynamic IPsec tunnels.

In a DMVPN network, there is a central hub device that acts as a focal point for the VPN connections. Each remote site, also known as a spoke, establishes a direct tunnel with the hub. The tunnels are dynamically built and torn down as needed, allowing for easy scalability and adaptability in the network.

DMVPN leverages routing protocols, such as EIGRP (Enhanced Interior Gateway Routing Protocol) or OSPF (Open Shortest Path First), to dynamically exchange routing information between the hub and spokes. This dynamic routing approach eliminates the need for static routing configurations, making it easier to add or remove sites without manual intervention.

One of the key benefits of DMVPN is its ability to optimize bandwidth usage. It achieves this through a technique called mGRE (multipoint GRE), which allows multiple spoke sites to share a single tunnel to the hub. This reduces the overhead associated with maintaining individual tunnels for each spoke, resulting in more efficient bandwidth utilization.

Overall, DMVPN provides a flexible and scalable solution for creating secure VPNs over IP networks. It simplifies network management, enhances scalability, and optimizes bandwidth usage, making it particularly suitable for large and geographically distributed networks.


The ISAKMP protocol (Internet Security Association and Key Management Protocol) is a framework for dynamically establishing security associations and cryptographic keys in an Internet environment.

Apply the same crypto ISAKMP policy, key, crypto IPsec Transform-set and Profile on the HQ (Hub) all sites (Spokes).

Each tunnel interface on the hub router is identified by a unique number, starting from 0 and incrementing for each additional tunnel interface. The “tunnel 0” interface is typically used as the default or primary tunnel interface in a DMVPN configuration.

The hub router’s “tunnel 0” interface is responsible for receiving and forwarding encrypted traffic from the spoke routers. It encapsulates and decapsulates the data packets, ensuring secure transmission across the VPN. The hub router uses routing protocols like EIGRP or OSPF to exchange routing information with the spoke routers, enabling dynamic and efficient routing within the DMVPN network.

Apart from the ip address on the Tunnel 0 interface, the only difference between the HQ (Hub) and the sites (Spokes) configuration are highlighted in the red box such as mapping the HQ tunnel ip address ( to its public ip address ( and the specification of the next hop server which is the HQ tunnel 0 ip address (

To leverage a dynamic routing protocol such as OSPF (Open Shortest Path First), setting the priority to 0 on the sites (Spokes) ensures that they will never be the DR or BDR in order to avoid LSA flooding and excluding the interface facing the internet from participating in OSPF.

EIGRP (Enhanced Interior Gateway Routing Protocol) or BGP (Border gateway protocol) works perfectly well over DMVPN, OSPF you cannot summarize within an area.  This is a problem because all of the routers on the DMVPN must be in the same area, and therefore we are unable to send a summary route from the hub down to the spokes and use NHRP overrides for spoke to spoke traffic.

NHRP (Next Hop Resolution Protocol) is an integral part of DMVPN (Dynamic Multipoint Virtual Private Network) and plays a crucial role in establishing and maintaining dynamic IPsec tunnels within the network.

In a DMVPN deployment, NHRP is used to provide efficient resolution of next-hop addresses. When a spoke router needs to send a packet to another spoke, it uses NHRP to determine the appropriate next-hop router, which is usually the hub router. NHRP allows spokes to dynamically discover the IP address of the next-hop router and establish a shortcut tunnel directly to it.

The NHRP process involves three main components:

  1. NHRP Clients (spokes): The NHRP clients are the spoke routers in the DMVPN network. They send NHRP requests to resolve the next-hop IP address of the destination spoke router.
  2. NHRP Server (hub): The NHRP server is typically the hub router in the DMVPN network. It receives NHRP requests from the spokes and provides the necessary information to establish direct tunnels between spokes.
  3. NHRP Resolution Requests and Replies: When a spoke router wants to send a packet to another spoke, it sends an NHRP resolution request to the hub router, specifying the destination spoke’s registered name or IP address. The hub router checks its NHRP cache to determine if it knows the mapping between the destination and its current IP address. If the mapping is found, the hub router sends an NHRP resolution reply to the requesting spoke, providing the necessary information to establish a direct tunnel with the destination spoke.

show dmvpn

show ip route ospf

Network reachability from site-2 and Site-3

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