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Multi-tenancy exists in some or other form in all kinds of networks. In an enterprise network it is viewed as separation of tenants based on business units and functions, departments, security and network policies and requirements of compliance. On the other hand, for a cloud service provider multi-tenancy refers to separate customers (tenants). Multi-tenancy provides a control boundary in terms of who controls what? In the NSX-T logical routing world, this function provides connectivity between the tenant logical network and underlying physical infrastructure.
In today’s topic we will learn about VMware NSX-T tiering functionality, need for multi-tiered routing, how routing works in multi-tiered architecture etc.
What is Tiering in VMware NSX-T
The NSX-T logical router allows traffic to flow East-west and Egress out (North-South) in public networks. The logical router is a virtual device which is distributed across transport nodes (ESXI / KVM hosts). Within NSX-T the tiering is supported so that multiple tenants can be given control of their own routing services, policies and NSX-T administrators can control policies and services at the tenant layer.
Related:
Tiering Structure
The tiering structure within VMware NSX-T is as follows:
VMware NSX-T Logical Routers
- Tier-0 Logical Router (Tier-0 Gateway) – This interface with the actual physical network in the North end of Tier-0 interfaces and is the top tier router. The dynamic routing protocols such as BGP can be configured here to exchange route information with physical routers. The south Tier 0 routing topology connects to the Tier 1 routing layer of tenant routing topology and receives routing information from the customer end. The Tier 0 routing layer sends default information to the Tier 1 routing layer.
- Tier-1 Logical Router (Tier-0 Gateway) – For public network access, the Northbound interface on tier 1 layer connects with tier 0 layer and Southbound interface hooks to logical switches created by tenant administrators.
Logical Router Components
- Distributed Router or DR
- Service Router (resides on VMware NSX-T Edge Nodes) or SR (act as a single router)
DR component location on transport nodes (ESXi / KVM hosts) is responsible for East-West Routing. Tier-0 Distributed Router (T0-DR) handles the First Hop Routing SR Component (NSX-T Edges) is used for North/South Routing
Distributed Router comprises Distributed Routing Components and centralized components known as Services Router (SR). DR Routing Components run as Kernel Modules in each Transport Nodes and edge nodes both.
Routing can be single tier or multi-tier.
NSX-T Single Tier Routing
Tier-0 Distributed Router (T0-DR) – Used by handles North-South Routing and handles First Hop Routing
Distributed Router comprises Distributed Routing Components and centralized components known as Services Router (SR). DR Routing Components run as Kernel Modules in each Transport Nodes and edge nodes both.
For configuring any of the below services:
- North-South routing
- DHCP/NAT
- Load balancing
- VPN
- Firewall gateway
- Bridging
NSX-T edge nodes need to be deployed hosting the service router. SR or service router will connect to external networks. Dynamic routing can be configured using BGP or static.
NSX-T Multi-tier Routing
- In multi-tier routing multi-tenant support is enabled
- The logical segregation between tenant router and service provider router is done
- Tier 0 is top tier gateway and tier 1 is bottom tier gateway
- Complete control of Tier 1 gateway is with the tenant
- Provide connectivity between tenants
- Direct connectivity to logical segments or VNIs
- Tier 1 gateway does east/west routing between tenants
- Tier 1 service routers within Tier 1 gateway can be implemented using DHCP, load balancing and Network address translation (NAT)
- Router link interface will automatically create connection to Tier 0 and Tier 1 gateway, interface subnet is created automatically.
ABOUT THE AUTHOR
I am here to share my knowledge and experience in the field of networking with the goal being – “The more you share, the more you learn.”
I am a biotechnologist by qualification and a Network Enthusiast by interest. I developed interest in networking being in the company of a passionate Network Professional, my husband.
I am a strong believer of the fact that “learning is a constant process of discovering yourself.”
– Rashmi Bhardwaj (Author/Editor)
