[c-nsp] L3 Switch as a BGP Gateway

[Jared Mauch]

Not really.

Think of the memory latency to traverse the stack.  Generally CPU <-> Memory bandwidth is measured at rates of speed and access higher than 1 or 10Gb/s.  Taking the PCI Express standard as a basic threshold of getting things into or out of the CPU, a 16-lane slot starts at 32Gb/s.

You start talking about the need to 'swap' as well as 'protect' in the stack against memory faults and failures.  This is certainly not ideal.  It may be useful for transient memory usage (e.g.: packet buffer memory, where one can expect the application or OS to do retransmits) but certainly not for your routing protocol to suddenly have half its resident memory go *poof* if the cable stack goes away.

- Jared

On Jun 27, 2011, at 4:30 PM, Murphy, Jay, DOH wrote:

> How about when you stack them as a logical switch. Couldn't one leverage the memory and processing of the stacking?
> 
> ~Jay Murphy 
> Sr. IP Network Specialist
> NM State Government
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> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jay Hennigan
> Sent: Monday, June 27, 2011 1:11 PM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] L3 Switch as a BGP Gateway
> 
> On 6/27/11 11:59 AM, Jason Greenberg wrote:
>> Can someone advise me as to why a 3750 L3 Switch (Metro Model) wouldn't outperform a 7300 series router as a multi-homed BGP gateway?  ISRs and Enterprise class routers are still quite a bit more expensive than the L3 Switches, but I'm starting to not understand why.   I understand that L3 switches are less feature rich on the routing end, but suppose that our ASAs are doing most of the complicated filtering.    I know it doesn't sound "right" to have a 3750G used in this manner, but I am having a hard time finding any real reason why not to do it.
> 
> The memory and number of routes are far too small to use these as a
> border router.  Generally adequate for iBGP to inject customer routes
> into your network but way too little for an Internet-facing border.
> 
> --
> Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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