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August 20, 2008
CCIE Wireless?
I just received a "general announcement" in my email about registering for the BETA CCIE Wireless written exam. Wow - yet another CCIE specialty arrives.If you'd like to see the CCIE Wireless Written Exam blueprint, click here.
Posted by JC at 4:23 PM | Comments (5) | TrackBack
August 15, 2008
GNS3 - The Full Story
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...).
Posted by JC at 4:03 PM | Comments (5) | TrackBack
August 14, 2008
Solarwinds Enters the NetFlow Fray...for Free?
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 :).
Posted by JC at 8:26 AM | Comments (6) | TrackBack
August 4, 2008
Dynamic Failover with IP SLA
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
Posted by JC at 1:36 PM | Comments (7) | TrackBack