Archive by Author
GNS3 - The Full Story
Posted on 15. Aug, 2008 by rivansystems.
It looks like someone has decided to write some awesome documentation / tutorials for GNS3. Answers plenty of the questions I had when I first got into it (installation, optimization, etc…).
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Solarwinds Enters the NetFlow Fray…for Free?
Posted on 14. Aug, 2008 by rivansystems.
Netflow has always been a topic of interest to me. It allows Cisco devices to track exactly how your network bandwidth is used. For example, using NetFlow allows me to see the applications (ports) using my Internet connection, how much bandwidth they are consuming, the source and destination IP addresses that are consuming the most traffic, and so on. Handy information!
Anyhow, Solarwinds has just released a new (free) tool that allows you to chart and graph all this information. This is definitely a plug for their enterprise Orion software which lets you manage bunches of devices…but hey, a free tool is still a free tool :).
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Dynamic Failover with IP SLA
Posted on 04. Aug, 2008 by rivansystems.
I just stumbled across this killer post on Shawn’s Blog that describes how to set up IP SLA to allow a static route to failover if pings to a specified internet host should fail. This is really useful if you have two ISPs (and thus, two default routes) where the router cannot detect a link failure. This is really common if you have a cable/DSL modem or some type of wireless connectivity. Here’s the basic config, taken directly from Shawn’s Blog:
ip sla 1 < The number 1 here is arbitrary, used only to identify this sla. It is otherwise knows as the operation number>
icmp-echo 4.2.2.2 < 4.2.2.2 is a DNS server that responds to pings out on the internet>
timeout 500 < This is how long to wait for a response from the ping>
frequency 3 < This is the repeat rate for the SLA>
ip sla schedule 1 start-time now life forever < This command says "start SLA 1 now and keep it running forever>
track 1 rtr 1 reachability < This comand creates the track object "1" and monitors the SLA 1>
now for the routing, we need to change the default route and associate it with the tracker
no ip route 0.0.0.0 0.0.0.0 1.1.1.1
and then put it back with the tracking
ip route 0.0.0.0 0.0.0.0 1.1.1.1 track 1
Then we need to add our secondary route
ip route 0.0.0.0 0.0.0.0 1.1.1.2 10
Now when the ping to 4.2.2.2 fails the primary route is removed and the secondary route with the higher metric becomes the default. The route will be reinstated when the connectivity is restored.
With the 12.4 and higher releases the commands have changed slightly but the “?” is your friend. If I receive requests for the syntax I will post it as well, but it is pretty easy to convert.
Here is the reference to the Cisco IP SLA documentation
http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a0080441845.html
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Best Cisco Laptop?
Posted on 30. Jul, 2008 by rivansystems.
I’ve been a “quasi-apple fan” for years…When they came out with the MacBook Pro, I bought the 17″ giganto-screen model and have been using it to configure Cisco devices ever since. Recently, I was at a client site…he pulled out an old Dell X200 12″ laptop to configure a Cisco router. I suddenly found myself [...]
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Automatic Err-Disable Recovery
Posted on 28. Jul, 2008 by rivansystems.
Someone showed me a great feature today. One of the constant pains in the network is when you get a port err-disabled on the switch. Regardless of how many times I see it, it always seems to be the last thing I check. There’s a little-known feature in the IOS called “err-disable recovery” which automatically turns a err-disabled switchport back on after 5 minutes (by default). The good news is that this command allows you to choose specific reasons where you’d like to re-enable the port, such as re-enabling ports disabled because of a port-flap instance but keeping mac-address security violations error disabled. Here’s the syntax to make it happen:
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VUE Releases Testing “Enhancements”
Posted on 24. Jul, 2008 by rivansystems.
These were rumored at the end of last year…looks like they have finally arrived! VUE Testing enhancements:
• Photo on Score Report and Web - On completion of a certification exam at the test center, candidates will receive preliminary score reports imprinted with their photos and unique authentication codes. The authentication code can be used to access a candidate’s official score online at Pearson VUE’s website usually within 72 hours of the examination. The online score report will also display the candidate’s photo. Candidates may share access to their online records with employers or other third parties.
• Forensic Analysis - Exam results and other testing data will be continuously analyzed by forensic software to detect aberrant testing behavior and to flag suspect exams for further investigation.
• Preliminary Score Report - All paper score reports will be preliminary, pending the results of forensic analysis, until official exam scores are posted to the Web usually within 72 hours of exam completion. Once the exam scores are official, candidates may use the authentication codes on their score reports to access the Pearson VUE website for score and photo verification.
That “Forensic Analysis” section looks pretty interesting. I wonder if they’re looking for the TestKing brain dump-style tests? I’m very curious!!!
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Another Great Resource
Posted on 21. Jul, 2008 by rivansystems.
Here’s another great blog/website resource to add to your list:
The site is well organized into interesting sections. I especially like the cheat sheet (for technology, not exams) and Network Monitoring / Utilities categories.
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Scheduling Periodic Config Backups in IOS
Posted on 19. Jul, 2008 by rivansystems.
Pretty cool article talking about using kron jobs on a Cisco router to schedule periodic configuration backups.
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CCNA Voice Exam Debrief
Posted on 08. Jul, 2008 by rivansystems.
Alright, this afternoon I took the CCNA Voice exam (aka Implementing Cisco IOS Unified Communications, 640-460). While I completely loathe brain dumps, I am all for getting a good idea of focus areas and the general feel for the exam, so that’s what I’ll give you here.
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More CCNA Voice Information
Posted on 30. Jun, 2008 by rivansystems.
Cisco has just launched a new learning site that has great info about all the new certifications. Click here to check it out.
One of the documents they posted to the site is excellent. It’s the CCNA Voice prep session from the Networker’s conference. If you want to get a good idea of the question types, topics, etc, download this document.