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JUNOS High Availability by Orin Blomberg, Senad Palislamovic, Kieran Milne, James Sonderegger

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Chapter 2. Hardware High Availability

Within networks, there are normally three roadblocks to high availability: hardware failures, software failures, and user-based configuration errors. Before we dive into the nitty-gritty details of how a string of acronyms (VRRP, ISSU, etc.) can improve the high availability of your network, we need to look at the hardware on which your network is based.

No matter how well designed a network is, if you’re missing a few key features in the hardware design all the protocol hacks, routing tips, and best common practices offered up in the networking books on your shelf may be useless. Let’s say that you have a set maintenance window for a bug scrub on your new router operating system, and you have tested the upgrade in the lab environment 10 times, but when you complete the upgrade, you discover that your routing engine (RE) is not booting. You will have to replace it and get your router running again before the maintenance window closes and calls start coming in from customers. To accomplish this task, it is vital that you have a way to smoothly replace hardware.

Any network design that is to provide high availability must be built on a solid foundation that offers stability, resiliency, and redundancy. Without such a foundation, the efforts of your team will be wasted on attempting to solve or mitigate issues through the use of complex redundancy protocol configurations or traffic engineering, when you and your customers would be better served by ...

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