Posts tagged: memory

Upgrading a Juniper J4350 to 2GB Compact Flash

This is somewhat of an impossibility, right?  Well, not really.  Although not technically supported by Juniper, we are able to go above the recommended 1GB Compact Flash size on J-series routers (at least J4350s).

This was performed on lab equipment, not production equipment.  I wouldn’t advise doing anything that would violate any manufacturer’s support agreement on production equipment.  Use this at your own risk – your mileage may vary, especially as it’s not following Juniper’s recommendations.  Phew – disclaimer finished – now let’s move on…

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Running two simultaneous instances of the Dynamips hypervisor

Running Dynamips can really tax system resources.  Often times it’s CPU utilization that’s first considered with several different routers.  While high CPU utilization can occur (shouldn’t be constant if the idle-pc values are adjusted properly for the different IOS images), I’ve run into more problems with memory utilization.

Each operating system has certain limitations in terms of how much memory space can be accessed by a single user-mode process.  Many people use one or another variant of the Microsoft Windows operating system (OS).  According to Microsoft (, the limit for 32-bit user-mode processes is 2GB.  This can easily be exceeded with a large Dynamips/Dynagen lab.  The following is how I’ve overcome this limitation, by using multiple Dynamips hypervisor instances.

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