oversubscribed ports for Juniper are a new feature

Neal Rauhauser neal at lists.rauhauser.net
Tue May 15 00:30:38 UTC 2007

   If you read up on juniper.net you'll see that in addition to the one 
gigabit port PIC there is now a card with four SFP ports but only a 
gigabit available via the backplane slot. This oversubscription of the 
slot is good when you have several little switches you wish to drive and 
don't need the full line rate.

  Sorry for the PDF but it seems to be the only way to see the information:


Hyunseog Ryu wrote:
> If I remember correctly from M5/M10,  they uses FEB 
> (built-into-Chassis FPC version), and each FEB (row) has restriction 
> up to 3.6Gbps rate.
> So total aggregated bandwidth can not go over this limit.
> If you install 4GE (4 of 1-port GigE PIC) in same FEB row, you can use 
> 0.9Gbps in average per PIC with max 1Gbps. :-)
> Also, 4GE PIC (single PIC with 4-port GigE) has limitation for up to 
> 1Gbps aggregated bandwidth, too.
> M7i/M10i has redundant RE options from M5/M10.
> So no differencce except M7i with built-in GigE into chassis.
> If you really wants to use GigE per trunk, you may have to use 
> PE-1GE-SFP instead of single quad-port GigE PIC.
> For memory, it may be sufficient with 768MB memory for now,
> But if I were you, I would go with 1.5GB with new RE.
> It's pain in the XXX to add more memory later from production system.
> If you are concerned about the budget, you can use after-market memory.
> Hyun
> Donald Stahl wrote:
>>>> choice. Layout here is such that I'd expect to use a single quad 
>>>> gigabit port
>>>> ethernet blade in each of a pair of M10i/M20 to achieve redundancy.
>>> he said 'blade' to which I read '4 pics in a FPC'... maybe it's a
>>> terminology thing? Neal?
>> The M10i doesn't have an FPC blade per se (it's built into the 
>> chassis) so in the context of the M10i I assumed "single quad gigabit 
>> port ethernet blade" meant a single card- though I could definitely 
>> be wrong. My knowledge of the Juniper line is sadly pretty limited.
>> -Don

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