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 Post subject: Why are my configurations so slow to update?
PostPosted: Mon Oct 13, 2014 8:22 pm 
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Joined: Mon Oct 13, 2014 8:11 pm
Posts: 1
Hello All,

I am currently studying for my ICND2. I have a home lab, which I have used for the majority of my studies, but now that I am reviewing Frame Relay I see that I am going to need some more complex topologies then what my three router lab can offer.

I am using the 2621 as my router as choice. (Only one I have an IOS for). Everything works fine for the most part. I had to mess around with the IdlePC values and the IdleMAX values to get the CPU usage down to a manageable level (under 5% now for a 4 router topology), but now that its not killing my CPU it works great. This software is really amazing. It seems like the sky is the limit as far as topologies go.

I do have one problem which is pretty annoying. I have noticed that these routers are very slow in taking changes. For example, when I configured R1 and R2 for a multpoint-to-point Frame Relay VC, it took like 3 minutes before I could ping across the VC.. All the configurations were right, it just took a long time for everything to apply it seemed like. This is a big annoyance because at the end of my configurations I'm left wondering if its just slow or if I messed up a configuration some where.. Is there something I can do to speed up this process??? I've got my IdleMAX value down from 1500 (default) to 200. I'm not sure exactly what this has done. (other then lower my CPU usage). Would this lowered value somehow be involve maybe???

Thanks for your input everyone. Its appreciated :)




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 Post subject: Re: Why are my configurations so slow to update?
PostPosted: Tue Oct 14, 2014 10:41 am 
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Joined: Fri Mar 05, 2010 11:33 am
Posts: 1494
Location: Australia
Here's a quote from the GNS3 Network Simulation Guide that might help you understand Idle-max and Idle-sleep.


Quote:
You will also see options here for IDLE-MAX and IDLE-SLEEP. These are also related to the Idle-PC value. Dynamips doesn't go to sleep every time the program counter hits the Idle-PC. It waits until it has hit the Idle-PC Idle-Max times before sleeping for Idle-Sleep milliseconds. That way the router still gets a chance to do the things it needs to do between visits to the Idle-PC value. If you adjust the Idle-Max too low or the Idle-Sleep too high, your emulated routers will slow down to a crawl, they will lose connections with their neighbors and bad things will happen.


So if you lower the Idle-Max value, your router is going to do a lot more sleeping that it would if you didn't change it. Which of course results in the router taking much longer to do things but of course it also means you CPU gets a cool ride too, because your router is not asking it to do stuff so often. Getting the right balance is a dark art indeed.

Disclaimer: I am the author of the GNS3 Network Simulation Guide



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GNS3 WorkBench-a VMware image of Ubuntu with GNS3 and VPCS installed and a collection of exercises/labs


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