[j-nsp] FE Memory Upgrade

[Matt Levine]

On May 10, 2005, at 2:14 PM, Richard A Steenbergen wrote:

> On Tue, May 10, 2005 at 12:04:07PM -0400, Eric Van Tol wrote:
>
>> I have no M7i experience, but I can tell you that an M20 with an  
>> SSB-E
>> and 64MB DRAM/8MB SRAM could only handle about 500K routes in the Rib
>> before it started to issue allocation errors.  768MB on the RE and  
>> 16MB
>> SRAM on the CFEB will do you fine, as long as you're not going to  
>> use it
>> to create 15 logical-routers, all with a copy of a full BGP table ;-)
>>
>> I received a good explanation from Juniper about how the memory
>> allocation in the SSB (or CFEB in your case) is handled (paraphrased
>> from JTAC):
>>
>
> That would be your SRAM that ran out, not the SSB DRAM. The DRAM is  
> used
> to hold the next-hop table, which can run out if you have a large  
> amount
> of arp entries on an ethernet interface for example.
>
> As it was described to me, the nhdb L2 descriptor size is hard  
> coded as a
> percentage of your DRAM. On a 64MB DRAM model, this comes out to  
> just over
> 50k:
>
>
> SFM2(xxx.xxx vty)# show nhdb zones
> Chip  Start   Size   Rsvd   Used/Hi Water/Total  Size  Name
> ----  -----  -----  -----  --------------------  ----  ----
>    0  20000  01000  00000               0/0/512     8  Multicast RTP
>    0  21000  02400  00000              0/0/9216     1  Multicast Lists
>    0  23400  04400  00006         176/180/17408     1  Next-Hop  
> Entries
>    0  27800  18800  0004b         856/885/50176     2  L2 Descriptors
>                                   ^^^^^^^^^^^^^
>
> If you have 50k arp entries on your system, it can exhaust the max L2
> descriptors. The Juniper answer is to buy a new switch board which has
> 128MB of DRAM on it. :)

And note that on the m160 each FPC is mapped to a individual SFM, so  
even though you have 200k across 4 sfms, you can fill up 50k on one  
and have 0k used on another..


>
> -- 
> Richard A Steenbergen <ras at e-gerbil.net>       http://www.e- 
> gerbil.net/ras
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> F8B1 2CBC)
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