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

As a CCNA or CCNP, one thing you ve got to get used to is that change is constant. Cisco regularly issues new IOS versions, not to mention the many different kinds of hardware they produce! While it s always nice to have "the latest and the greatest" when it comes to routers, switches, firewalls, etc., we have to be prepared for the fact that not all our clients are going to have that latest and greatest!
For instance, there are still quite a few Catalyst 5000 switches out there humming away, and if you re used to working on IOS-driven switches like the 2950, the same command can have dramatically different results.
Let s say you re going to examine the spanning tree protocol (STP) setup of a new client. You re used to working with newer 2950 switches, and you ve always run show span on those switches to display spanning-tree information. Then, you run show span on a Catalyst 5000 - and something like this shows:
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 going on here?
The command show span on a 5000 will not show spanning tree stats - instead, what you re going to see are statistics relating to Switched Port ANalyzer (SPAN). Surprise!
Consider an example where you re used to running show span on 5000 switches to see SPAN information. When you run that on a 2950, you know now what you re going to get - spanning tree information! To get SPAN stats on a 2950, you ll need to run show monitor session, 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
As a CCNA and CCNP, this is one of those things you just have to get used to. Commands are going to be different, sometimes radically so, between models. That s why you need to be adept with both IOS Help and Cisco s online documentation site. IOS Help is easy, but the online doc site take a little getting used to. Once you learn how to navigate that site, a world of Cisco knowledge is at your fingertips.
Besides, when you sit for the CCIE lab exam, that will be the only friend you have! And a valuable friend it can be - you re just going to have to trust me on that one. :)
Chris Bryant, CCIE 12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.
You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.
For a FREE copy of his latest e-books, How To Pass The CCNA and How To Pass The CCNP , visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! And coming in 2007 -- Microsoft Vista certification from The Bryant Advantage!



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