From: sheherezada@gmail.com
Date: Tue Nov 06 2007 - 14:33:56 ART
Joe,
I know that "we all know", but why? It's not always possible to have
Layer 3, so I think it's worth asking.
BTW, the diameter of a broken well known topology (with two Layer 2
aggregation switches and 'n' access switches linked to both) is 5
(when you break the link between aggregation _and_ one uplink). It
looks like a triangle, but it's not.
So, any scary failure scenarios (of a medium sized, multiple Layer 2
ring topology)?
Mihai
On Nov 6, 2007 4:35 PM, Joseph Brunner <joe@affirmedsystems.com> wrote:
>
> Actually I have seen diameters greater than 7 just recently (perhaps as much
> as 11).
>
> I believe the original standard was written at a time when they didn't have
> what we know as a switch (hubs, translational bridges, etc.)
>
> Its far better to layer 3 route as we all know, so why not just keep your
> diameter around 2 (access to distribution) then route after that?
>
> Layer 3 switches today can be had for dirt prices (ok, maybe dell/hp)...
>
> -Joe
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> sheherezada@gmail.com
> Sent: Tuesday, November 06, 2007 4:43 AM
> To: Cisco certification
> Subject: OT: STP diameter
>
> Hi,
>
> I suppose that daisy-chaining switches beyond 3 or 4 bridges is not
> recommended, because I have never saw this in a reference design. I
> also know the IEEE 802.1D recommendation of having no more than 7
> bridges diameter with the default STP timers. However, can anyone
> tell me WHY having a 7-8 bridge loop topology is such a bad idea in
> practice after all, especially with RSTP, apart from possibly
> degrading convergence time? I am not saying that this would be good,
> I just want to clear the FUD. My understanding is that the
> theoretical diameter is given by the Max Age value, hence we may have
> a maximum diameter of 20.
>
> Thanks,
>
> Mihai
>
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