Design Guide

4
LAN Baseline Architecture Overview—Branch Office Network
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Multilayered Branch Architecture
Figure 1 shows the various layers of a branch multilayered architecture, and also shows various ways in
which a branch office network can be designed.
The architecture should be highly available as well as scalable. Based on the products available, and the
scalability and high availability requirements, the architecture can be modified without losing the
distinct services offered by each layer. The various possibilities are shown in
Figure 1. The most flexible
option is the second option (II) in Figure 1, which provides high availability as well as scalability. The
number of access switches supported can be scaled easily, thereby increasing the number of users.
The distribution layer can be collapsed into the edge, or the distribution and access layers into the edge,
based on high availability or scalability requirements.
Figure 1 Layers of a Multilayered Branch Architecture
Note Small branch LAN offices can use integrated switching at the edge, and might not have to resort to a
multilayer architecture, depending on the number of users and the size of the office. Also, some of the
integrated switches for ISR, do not provide the advanced spanning tree and security features that are
important for quick convergence in case of switch or link failure in a highly available branch office
architecture. High availability and scalability requirements are met by adopting a multilayered
architecture. Medium and large branch offices must adopt some variety of multilayer architecture.
Services
Figure 2 shows the services at various layers of the branch architecture.
End
Device
I
II
III
Management
IV
Security
LAN/WLAN
IP Communications
WAN
Applications
Edge Distribution Access (Wired/Wireless)
IP
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