Specifications

CHAPTER 5

Implementing High Availability

n Disaster recovery and business continuity plans

n Evaluating the security impact of a proposed change

Tools

A well-designed, highly available network can have a failure without it being noticed by users. It is important to have

tools in place to monitor the network and send alerts when a failover occurs. Monitoring can also help spot problems as

they begin to occur, enabling you to be proactive in your network management. There are many third-party tools available

for this; some IOS tools are discussed in later sections of this chapter.

Good documentation is a critical tool to have. Good documentation includes up-to-date network diagrams with network

addresses, VLAN information, and interface information. Important servers, applications, and services should be noted.

Document not only HOW the network is designed, but also WHY it is designed that way.

Resiliency and High Availability

A highly available network is a resilient network. A resilient network employs various methods to allow it to recover and

continue operating in the event of a failure. Resiliency leads to high availability through the following components:

n Network-level resiliency (the focus of this book): This includes redundant links and redundant devices, but it

doesn’t stop there. Those devices must be configured so they fail between devices, or links, quickly.

n System-level resiliency: This includes redundancy within the hardware, such as dual power supplies, and cold-

standby parts, such as extra stackable switches or switch modules. It also includes features within the hardware that

enable fast failover.

n Network management and monitoring: You need to detect a failure immediately and be informed of the actions

taken automatically to remediate it.

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CCNP SWITCH 642-813 Quick Reference by Denise Donohue