Cisco Routers for the Desperate: Router and Switch Management, the Easy Way 2nd Edition by Michael W. Lucas (2009) Paperback by Michael W. Lucas

Author:Michael W. Lucas [Lucas, Michael W.]
Language: eng
Format: epub
Amazon: B011DC2AOC
Publisher: No Starch Press
Published: 1709-07-15T00:00:00+00:00

Chapter 6. IOS Changes

Cisco's Internetwork Operating System (IOS) is the brains of any Cisco router. IOS provides the command line, interface device drivers, routing software, and all the other bits that make a router do more than draw power and generate heat. Cisco continuously maintains and updates IOS, adding more features as they become useful and stable. If you want some of Cisco's nifty new functionality, you'll probably find it in an IOS upgrade.

The only reasons to upgrade are for security, stability, or required features. While running the latest IOS might enhance your geek credibility, that is insufficient motivation for staying up all night hoping that the "bad upgrade recovery process" works. I advise you try Cisco-recommended workarounds or alternatives before attempting an upgrade. A successful upgrade only causes a few minutes of downtime, but a failed upgrade can take the router out of action for several hours.

If everything goes perfectly, the upgrade process is quick and easy: get the new IOS file onto the router's flash disk and reboot.

SMARTNET AND IOS UPGRADES

Do not attempt an IOS upgrade without a SmartNet support agreement! An IOS upgrade gone bad might leave your router completely unusable without advanced help. I've had upgrades where the router could not find its own network interfaces or wouldn't boot at all and was stuck in rommon (BIOS) mode. Cisco has many different versions of IOS for each router. Installing the wrong IOS can turn your expensive router into an expensive chunk of metal and plastic that requires expert help to repair.

Cisco Security Notifications

Every so often, some bright person discovers a security flaw in the Cisco IOS. Because the router is the first point of entry onto a network, no security device on your network can protect it, which means that when a security hole is discovered in IOS, you may have to upgrade the router to keep intruders out.

Cisco announces security issues through a customer mailing list and through security mailing lists such as BugTraq.

If you're not already on a mailing list that gets Cisco security announcements, you should sign up for Cisco's customer security announcements list, [email protected]. Send an email to the address [email protected]. You'll receive a reply giving you instructions on how to confirm your subscription and a copy of the list policy.

Read all Cisco security alerts carefully. If you're not using the affected functionality mentioned in an alert, or if the problem doesn't affect your equipment, don't worry about it. But if the alert affects you, schedule a maintenance window to take the router down and upgrade the IOS.

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