Re: mac-address ageing per vlan

I have always found this to be an interesting topic ... mainly, because it
occurs automatically and we do not think much of it (except for CCIE
studies!)

Here is the link I assume you are referring to?
http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_se/configuration/guide/swstp.html#wp1169222

Johnny mentioned the command to set the aging time manually. I think he
answers your question.

- Team - keep me honest here ...

A couple of thoughts around this and to try and keep things clear (at least
in my head).

W/ rapid spt the mac address is immediately deleted when a TCN is learned,
no need to rely on the aging timers per mac address. MSTP is built on rapid
stp, so it also performs the same.

When spt needs to converge different paths may exist throughout. What would
happen if all the mac addresses are learned over an interface that is no
longer the forwarding one? Some confusion within the switch perhaps;
especially when it starts to learn mac addresses over different interfaces.

So the switch should age these mac addresses per the forwarding time, and as
the documentation mentions. This makes sense for STP.

Does the forwarding time have affect with rapid and or mstp for alternate
links? Humm ... not really. What does this mean for the aging times? My
understanding is that these are aged out immediately for the vlans that were
affected.

Anyone see this in the docs or a lab test? I would lab test it but I have
no time today till maybe late tonight.

Can you believe I am still working on leaves and honey-do lists? Ok,
honey-do lists of course ... these never end, but still raking leaves?
Sadly true ...

I feel like Fred Sanford from 'Sanford and son' crying about my back and
heart ... no one seems to care. ;-) ... crickets and tumbleweeds are all I
hear and see when I say these things ... oh humm ... it is hard to be me.
lol

Andrew Lee Lissitz

On Sat, Nov 14, 2009 at 1:11 AM, Johnny B CCIE <jbccie_at_gmail.com> wrote:

> conf t
> mac address-table aging-time x vlan xx
>
> The default value x is 300 seconds = 5minutes.
> If you use x = 0, then you have disabled aging for the vlan in question.
>
>
>
> On Sat, Nov 14, 2009 at 12:42 AM, Abraham, Tharak
> <tharakabraham_at_gmail.com> wrote:
> > Gents,
> >
> > Could you explain how to enable mac-add ageing for a particular vlan ?
> >
> > Just read that accelerated-ageing for a particular vlan can be linked
> with
> > STP for that vlan with the forward time.
> > i.e spanning-tree vlan x forward-time y
> >
> > Could someone add more thoughts on this ?
> >
> > Tharak
> >
> >
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-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net