At the core of NSX lies the Distributed Logical Router (DLR), a key component that provides advanced routing capabilities within the virtualized network infrastructure. In this blog post, we will explore the NSX DLR in detail, understanding its purpose, functions, use cases, and how it enhances network virtualization. Let's dive into the world of NSX Distributed Logical Router.
What is NSX Distributed Logical Router (DLR)?
The NSX Distributed Logical Router (DLR) is a software-based router that operates in the virtualized environment provided by VMware's NSX platform. The DLR is deployed as a virtual appliance, enabling routing services within and between logical networks in the virtual infrastructure. It provides scalable and high-performance routing capabilities while maintaining network isolation and security.
A logical router can have eight uplink interfaces and up to a thousand internal interfaces. An uplink interface on a DLR generally peers with an ESG, with an intervening Layer 2 logical transit switch between the DLR and the ESG. An internal interface on a DLR peers with a virtual machine hosted on an ESXi hypervisor with an intervening logical switch between the virtual machine and the DLR.
The DLR has two main components:
The DLR control plane is provided by the DLR virtual appliance (also called a control VM). This VM supports dynamic routing protocols (BGP and OSPF), exchanges routing updates with the next Layer 3 hop device (usually the edge services gateway) and communicates with the NSX Manager and the NSX Controller cluster. High-availability for the DLR virtual appliance is supported through active-standby configuration: a pair of virtual machines functioning in active/standby modes are provided when you create the DLR with HA enabled.
At the data-plane level, there are DLR kernel modules (VIBs) that are installed on the ESXi hosts that are part of the NSX domain. The kernel modules are similar to the line cards in a modular chassis supporting Layer 3 routing. The kernel modules have a routing information base (RIB) (also known as a routing table) that is pushed from the controller cluster. The data plane functions of route lookup and ARP entry lookup are performed by the kernel modules. The kernel modules are equipped with logical interfaces (called LIFs) connecting to the different logical switches and to any VLAN-backed port-groups. Each LIF has assigned an IP address representing the default IP gateway for the logical L2 segment it connects to and a vMAC address. The IP address is unique for each LIF, whereas the same vMAC is assigned to all the defined LIFs.
Functions of NSX Distributed Logical Router (DLR):
a) East-West Routing: The primary function of the NSX DLR is to facilitate routing between virtual machines and services within the virtualized network infrastructure. It enables seamless communication between workloads located on different logical switches, allowing for efficient east-west traffic flows.
b) North-South Routing: The DLR also handles north-south routing, which involves the exchange of traffic between virtualized networks and external networks. It connects virtual networks to physical networks, providing access to resources outside the NSX environment, such as the internet or external data centers.
c) Dynamic Routing: NSX DLR supports dynamic routing protocols, including OSPF (Open Shortest Path First) and BGP (Border Gateway Protocol). These protocols enable the DLR to exchange routing information with other routers, both virtual and physical, and dynamically determine the optimal path for data packets.
d) Logical Network Segmentation: With the NSX DLR, organizations can achieve logical network segmentation by creating separate logical switches and routing domains. The DLR ensures that traffic flows between these logical segments follow the defined routing policies, providing isolation and security.
e) Load Balancing: The DLR offers load balancing capabilities, distributing traffic across multiple virtual machines or services within a logical switch. This improves performance, enhances resource utilization, and ensures high availability for applications and services.
Use Cases and Benefits of NSX Distributed Logical Router (DLR):
a) Micro-Segmentation: The NSX DLR plays a crucial role in implementing micro-segmentation within the virtualized environment. It enables organizations to create separate logical networks and routing domains for different applications or business units, ensuring strict isolation and security controls between them.
b) Multi-Tier Application Architecture: With the DLR, organizations can design and implement multi-tier application architectures within the virtualized network. Each tier, such as web, application, and database, can reside on separate logical switches, and the DLR facilitates routing and connectivity between them while enforcing security policies.
c) Hybrid Cloud Connectivity: The NSX DLR enables seamless connectivity between on-premises environments and public clouds. Organizations can use the DLR to establish secure connections to cloud service providers, ensuring consistent network policies and enabling workload mobility across hybrid cloud environments.
d) Network Services Insertion: The DLR supports the insertion of network services such as firewalls, load balancers, and intrusion prevention systems into the traffic path. This allows organizations to apply security policies and advanced network services at the routing level, enhancing the overall security and functionality of the virtualized network.
The NSX Distributed Logical Router (DLR) represents a critical component in VMware's NSX platform, providing advanced routing capabilities within the virtualized network infrastructure. With its ability to handle east-west and north-south traffic, support dynamic routing protocols, and enable logical network segmentation, the DLR empowers organizations to build secure, scalable, and agile networks.
By leveraging the NSX DLR, organizations can achieve micro-segmentation, multi-tier application architectures, hybrid cloud connectivity, and service insertion. It plays a vital role in enhancing network performance, enabling efficient traffic flows, and enforcing security policies.
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