Design Guide

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LAN Baseline Architecture Overview—Branch Office Network
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Multilayered Branch Architecture
Figure 5 Highly-Available LAN Design with No Layer 2 Loops
This topology uses stackable switches at the distribution layer instead of two distribution switches
running Hot Standby Routing Protocol (HSRP). This topology is highly available and scalable. In this
topology, the Layer 3 redundancy is built into the stack. High availability between access and
distribution is provided by using EtherChannels. This topology has no Layer 2 loops. However, spanning
tree should be enabled and configured to mitigate any accidental Layer 2 loops. Layer 2 at the access
layer also makes the integration of various technologies easier, and also provides more flexibility. If
appliance devices have to be used rather than service capabilities on the ISR for higher throughput
reasons, the hierarchical design with Layer 2 at the access layer provides more flexibility to integrate the
appliances.
Layer 3 at the Access
Layer 3 in the access brings a different perspective to the solution. In this solution, routing is enabled on
the access switch but still provides the capability to put end users in different VLANs. Routing on the
access switch implies using a platform that supports routing and switching.
Figure 6 provides some
details of a Layer 3 access solution. The access switch provides equal cost multiple paths to the
core/edge device. Under failure circumstances, the convergence can very well be in sub-seconds with
EIGRP.
Layer 3
Layer 2
Access
Distribution
Stackwise
switches
Core
Or
Edge
Access Point
Stack Ring
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