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My Dynamips experience on Linux posted 10/16/2007
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Hi all,
I have been preparing for the lab for 6 months using my desktop: Core2Duo,
with 2Gig + Windows 2003. But the performance was severe and i was not able
to complete the labs without adding another Pentium D 2.66 with 1Gig to the

After my post for a help on GS, i was directed to Linux. I was so desperate
that i switched instantly using another spare harddisk into my Core2Duo

I have installed Fedora-Core 6 + its development Libraries + GDE(just for

I have started my 2 Dynamips instances and placed the server in init-level 3
(multiuser text mode) to save memory and resources required for switching to
GUI Mode. No Kernel Modifications as i donot want to spend time on that, if
its worth-it do tell me.

I have all my Dynagen Configuration files onto my Laptop running Windows XP,
in the configuration i changed nothing but the following:
1. IP Addresses and Dynamips Server Ports that were assigned to Linux.
2. Working Directory Paths from C:\ccie\....... to \ccie\.... ( this
directory i made on my linux system)
3. Re-calculated the IDLEPC Values for all of the IOSes which i was using.
4. Copied any existing data to Linux using WinSCP.

Now about the Performance Experience.
1. Startup Performance: I have seen a considerable speedup in loading of
routers when i issue start /all command. In windows occasionally my dynamips
got crashed when i issue start /all so i had to start all routers
one-by-one. but no crashes in linux have been experienced so far.

2. Number of Instances: Previously i was able to run only 6 Instances of
3640 with Full Load (IGP + EGP + Redistribution + Authentication + L2) on
which the CPU will touch 90 - 100%. Now on the same load its under 50%. I
did ran the exact same lab with same config. which means i can run more
instance as required.

3. Response: Previously since my cpu load was 100% i got a very slow
terminal response from routers such as on show run but on linux it flies. I
use SecureCRT on Windows to get into  router consoles.

4. Scenario Loading: I use mmap = true and ghostios = true also. When i
started my dynagen config the PC took a while loading the scenario, starting
stopping ghost images etc.. but on Linux it does the same with much more
speed and i get the console prompt almost instantly.

5. Memory Usage: I use 3640 + 128M RAM and 3620 + 64M RAM normally. But my
Windows System did more swapping then this linux one. Linux always had 500M
available while windows were on 100M. I guess Windows memory management is
the problem there.

6. Performance Issues: I did noticed that my EIGRP neighbor relationships
kept failing, OSPF enabled routers made adjacencies in a while due to high
load of CPU but now it works fine with Linux.

I have also read somewhere that FreeBSD would be more efficient than Linux
and i do have experience on it but i dont have time to try FreeBSD. If
someone already has please post your comments about it.

I need a solution to the Terminal like SecureCRT in Linux. Because if i
switch my Windows XP to Linux which one should i use. so if anyone has some
comments do post about it.

Thanks to Scott Vermillion for directing me to Linux and the Brians of IE
for making it so easy to start with Dynagen / dynamips as a beginner on
Windows. And most importantly thanks to Chris and Greg for such a nice

Farhan Anwar