CCIE Written Blueprint: 1.1.a Describe basic software architecture differences between IOS and IOS XE

Wed 06 August 2014

I have had an idea. I decided the best way to focus on the CCIE topics to study for the written exam (and try and reign myself in from just reading the "interesting" stuff!) is to aim for the exam topics...if I know all of them, how can I fail?

The exam topics are available here: Cisco CCIE Written Exam Topics

I have copied these out in to a word document, and I intend to write a small paragraph about each topic. It's concise, consolidated and easy to revise from, yet makes me read tons of stuff I wouldn't usually read to learn enough information.

So to start...here is section 1.1.a: Describe basic software architecture differences between IOS and IOS XE.

1.1.a Describe basic software architecture differences between IOS and IOS XE

http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/ios-xe-3sg/QA_C67-622903.html

In IOS XE, IOS 15.0 runs as a single daemon inside a Linux operating system. Other system functions now run as discrete separate processes in the host OS. As well as stability benefits, this allowed load balancing across multi-core CPU’s.

1.1.a (i) Control plane and Forwarding plane

Control and data plane can be further separated, as the drivers for the ASICs can be external from the IOS process. There are a standard set of API’s available to the control plane processes provided by the Forwarding and Feature Manager (FFM). In turn, the FFM programs the data plane via the Forwarding Engine Driver (FED).

1.1.a (ii) Impact to troubleshooting and performances

Separate processes allow for better fault isolation and reliability – one process dying won’t necessarily kill the box.

Supports multithreading and multicore CPU’s.

Provides the same look and feel as IOS.

Wireshark and Mediatrace included.

1.1.a (iii) Excluding specific platform's architecture

IOS XE allows the platform dependent code to be abstracted from a single image. Because the drivers are outside of IOS, this enables a more platform independent IOS process.

Non-IOS applications can be either tightly integrated or run alongside IOS on the same platform. “Service Points” are available for integration with IOS.

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