A variance of 2 means that you will use the best path
any any other path that is less than twice the best
metric.
In the case of 2 paths, you will then send twice as
much traffic over the better path.
BE VERY CAREFUL with variance, how it's implemented
depends on whether the router is process switching or
fast switching.
For process switching, two packets are sent on the
better path for every one packet on the other path.
For fast switching, twice as many destinations are
cached against the better path. But what if there is
very little traffic to many of the destinations cached
against the better path? This will result in what is
termed pinhole congestion with too much traffic going
over the slower path.
Personally I do not like the variance feature. I have
never seen it used on a real network- for good reason.
Also, I would say that this is why your BSCN
instructor did not pay much attention to it.
Regards,
Cormac Long CCSI#21600
http://www.cormaclong.com
--- Babashola Madariola
<[EMAIL PROTECTED]> wrote:
>
>
> So how do you know the variance value, do you for
> instance, just guess the value
> 2?
> Assuming you have more than 10 paths to a
> destination, how do you arrive at the
> variance value, what criteria do you use?
>
>
> ---------------------- Forwarded by Babashola
> Madariola/C/Africa/Mobil-Notes on
> 07/06/2000 10:01 AM ---------------------------
>
>
> "McCallum, Robert"
> <[EMAIL PROTECTED]> on 07/06/2000
> 07:07:29
> AM
>
> Please respond to "McCallum, Robert"
> <[EMAIL PROTECTED]>
>
> To: "'Brandon Carroll'" <[EMAIL PROTECTED]>,
> [EMAIL PROTECTED]
> cc: (bcc: Babashola
> Madariola/C/Africa/Mobil-Notes)
> Subject: RE: Variance Question
>
>
>
>
>
> Variance command is used to load share over unequal
> paths. i.e. a 1mb and a
> 2 mb circuit, in normal routing terms the 2mb
> circuit would be used all the
> time (unless specified otherwise). Putting a
> variance in this case of 2
> will allow any the above circuits to load share.
> Because 1 * 2 = 2.
>
> -----Original Message-----
> From: Brandon Carroll [mailto:[EMAIL PROTECTED]]
> Sent: 06 July 2000 22:52
> To: [EMAIL PROTECTED]
> Subject: Varience Question
>
>
> Hello,
>
> I am in the BSCN class right now and touched on the
> term "Varience"
>
> Could someone pleas explain this to me. I don't
> feel it was covered very
> well and I am actually feeling a bit lost on this.
>
> Thanks,
>
>
>
>
> ___________________________________
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=====
http://www.cormaclong.com
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