Basic Datacenter Switching

In this article, I am going to talk about the traffic flow or you can say the representing the logical topology using virtualized VDC. Before we will start with the further discussion just have a look on the basic datacenter environment with all the four layers. 

Logical topology example using services VDC sandwich physical model

Lets talk about the topology and the traffic flow

• Layer-2 only services chassis with transparent service contexts
• VLANs above, below, and between service modules are a single IP subnet
• Sub-aggregation VDC is a layer-3 hop running HSRP providing default gateway to server farm subnets

Fig 1.1- Logical Topology example using VDC model

• Multiple server farm VLANS can be served by a single set of VLANs through the services modules
• Traffic between server VLANs does not need to transit services device, but may be directed through services using virtualization

Logical Topology to support multi-tier application traffic flow

• Same physical VDC services chassis sandwich model
• Addition of multiple virtual contexts to the transparent services modules
• Addition of VRF routing instances within the sub-aggregation VDC

Fig 1.2- Logical Topology example using VDC model multi-tier application Flow

• Service module contexts and VRFs are linked together by VLANs to form logical traffic paths Example Web/App server farm and Database server cluster homed to separate VRFs to direct traffic through the services