Cisco CCNA / CCNP Certification Exam: Same Command, Different Results

May 18
21:15

2024

Chris Bryant

Chris Bryant

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As a CCNA or CCNP, you must be prepared for the unexpected. In the field, using the same command on different devices can yield vastly different results. Discover why this happens and how to manage it effectively, with insights from Chris Bryant, CCIE #12933.

The Ever-Changing Landscape of Cisco Devices

One of the key challenges for CCNA and CCNP professionals is adapting to constant changes. Cisco frequently releases new IOS versions and a variety of hardware,Cisco CCNA / CCNP Certification Exam: Same Command, Different Results Articles from routers and switches to firewalls. While having the latest technology is ideal, not all clients will have the most up-to-date equipment. For instance, many organizations still use older Catalyst 5000 switches, which can behave differently from newer models like the 2950.

Case Study: Spanning Tree Protocol (STP) Commands

Imagine you're tasked with examining the Spanning Tree Protocol (STP) setup for a new client. You're accustomed to using the show span command on 2950 switches to display spanning-tree information. However, when you run the same command on a Catalyst 5000 switch, you might see something unexpected:

switch (enable) show span

Destination : Port 6/1
Admin Source : Port 6/2
Oper Source : Port 6/2
Direction : transmit/receive
Incoming Packets: disabled
Learning : enabled
Multicast : enabled
Filter : -
Status : active

Total local span sessions: 1

What's Happening Here?

The show span command on a Catalyst 5000 switch does not display spanning-tree statistics. Instead, it shows statistics related to the Switched Port Analyzer (SPAN). This can be surprising if you're not prepared for it.

Different Commands for Different Devices

If you're used to running show span on a 5000 switch to see SPAN information, you'll get spanning-tree information when you run it on a 2950. To get SPAN stats on a 2950, you need to use the show monitor session command followed by the SPAN session number:

SW1#show monitor session 1

Session 1
---------
Type : Local Session
Source Ports :
Both : Fa0/1
Destination Ports : Fa0/2
Encapsulation : Native
Ingress: Disabled

Adapting to Different Command Outputs

As a CCNA or CCNP, you must adapt to different command outputs across various devices. Commands can vary significantly between models, making it essential to be proficient with both IOS Help and Cisco's online documentation.

Utilizing IOS Help and Cisco Documentation

IOS Help is straightforward, but navigating Cisco's online documentation can be challenging initially. Once you master it, a wealth of Cisco knowledge becomes accessible. This skill is invaluable, especially when preparing for the CCIE lab exam, where it might be your only resource.

Interesting Stats and Facts

  • Cisco's Market Share: As of 2021, Cisco holds approximately 51% of the global Ethernet switch market and 33% of the enterprise router market (source).
  • Device Diversity: Cisco offers over 1,000 different models of switches and routers, each with unique features and command sets (source).
  • Certification Popularity: Over 1 million individuals have earned a Cisco certification, making it one of the most recognized IT certifications globally (source).

Conclusion

Navigating the complexities of different Cisco devices and IOS versions is a crucial skill for CCNA and CCNP professionals. By understanding the nuances of various commands and leveraging Cisco's extensive documentation, you can effectively manage and troubleshoot diverse network environments. This adaptability not only prepares you for real-world scenarios but also sets a strong foundation for advanced certifications like the CCIE.

For more information on Cisco certifications, visit the Cisco Learning Network and explore their comprehensive resources.