Flash memory and SDRAM size for cisco 12816 router PRP-2

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Oct 26th, 2008
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I want to choose a flash memory and a SDRAM for a cisco 12816 router PRP-2 that used in core of a network that has extensive load but i can't find any document that recommend a size for it. Also the router has about 10*10Ge, 6*STM64 and other interfaces.


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Giuseppe Larosa Sun, 10/26/2008 - 06:16
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Hello Saied ,

I've in production network with 2GB RAM and a 1GB ATA PCMCIA card on a 12410 that receives three full BGP tables from ISPs

NAME: "slot 8", DESCR: "PRP-2"

PID: PRP-2 , VID: V02, SN: SAD09310613

Hope to help


favaparsCO Sun, 10/26/2008 - 07:16
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Hello Giuseppe,

Thanks for your attention. Are there other features that must be considered when selecting flash and memory for router.



Giuseppe Larosa Sun, 10/26/2008 - 13:31
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Hello Saied,

on a GSR 128016 the duty of PRP-2 is to mantain all routing protocols information including adjacencies and to build the CEF table and to keep in sync its copy of the CEF table with the CEF table copy that is in each linecard

(this is CEF distributed)

So the memory of the CPU has to be big enough to host all routing protocols processes, the IP routing table, the ARP table and the CEF table.

If you have a linecard with 10GE ports and 512MB of RAM I would expect PRP to have at least 1GB of RAM just to be sure it has enough RAM.

However, if you know that your router will never handle an high number of routes (and you need to count also MPLS L3 VPN and other MPLS services) you can use a PRP-2 with standard memory that probably is 1GB.

For the flash the minimum requirement is to able to host the IOS image to be loaded at startup so probably a 64 MB is enough.

A bigger flash like the one I have on this 12410 can allow to host multiple versions of IOS (each one is roughly 23-24 MB with 12.0(32)SY) and to have space to host a core dump in case of crash.

Hope to help



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