Information Technology Reference
In-Depth Information
10 Gigabit Ethernet
Gigabit Ethernet or Etherchannel
Backup
Campus Core
DC
Core
DC
Aggregation
Aggregation 2
Aggregation 3
Aggregation 4
DC
Access
Layer 2 Access with
Clustering and NIC
Te a m i n g
Blade Chassis with
Passthru Modules
Mainframe
with OSA
Blade Chassis
with Integrated
Switch
Layer 3 Access with
Small Broadcast Domains
and Isolated Servers
Figure 4-8
Enterprise Data Center Infrastructure Overview
Defining the DC Access Layer
The data center access layer's main purpose is to provide Layer 2 and Layer 3 physical
port density for various servers in the data center. In addition, data center access layer
switches provide high-performance, low-latency switching and can support a mix of over-
subscription requirements. Both Layer 2 and Layer 3 access (also called routed access) de-
signs are available, but most data center access layers are built using Layer 2 connectivity.
The Layer 2 access design uses VLAN trunks upstream, which allows data center aggrega-
tion services to be shared across the same VLAN and across multiple switches. Other ad-
vantages of Layer 2 access are support for NIC teaming and server clustering that requires
network connections to be Layer 2 adjacent or on the same VLAN with one another.
Key
To p i c
Figure 4-9 highlights the data center access layer in the overall enterprise architecture.
The Spanning Tree Protocol (STP) manages physical loops that are present in the Layer 2
design. Currently, the recommended STP mode is Rapid per-VLAN Spanning Tree Plus
(RPVST+), which ensures a logical loop-free topology and fast convergence.
