01-07-2008 05:57 AM - edited 03-05-2019 08:19 PM
Hi, I heard talks about the spanning-tree distance to be max 7. Is this still true? It has a uge impact on the design we are making.
Thx!
Marc
01-07-2008 06:05 AM
You have a network that is more than 7 hops diameter? Wow!
In principle, you should be able to set your timers to cope with a diameter greater than 7 hops. The "root" macro will not help you wih more than 7 hops - you will have to do the calculations yourself.
But it will converge at snails-pace. Frankly I would urge you to reconsider your design if you have a layer-2 that spans more than 7 hops.
I wonder if there is a misunderstanding here. Do do mean hops-in-a-line and not total switches, don't you?
Kevin Dorrell
Luxembourg
01-07-2008 06:09 AM
I mean hops-in-a-line, total switches is about 150 +
01-07-2008 06:10 AM
Hi Marc,
Let me try to put my thaughts.If you have a core switch and connected to this switch are 10 switches so each switch has one connection to the core switch this is a diameter of 1.
It's not the number of switches it's how the are connected. So
core switch -> switch1 -> switch2 -> switch3.
If you have switches connected in the above fashion then your diameter is 3. Does your topology goes 7 line above?
With IEEE 802.1d,recommended consideration when designing the network with STP is not more than 7 hops. On the default timer parameters STP is expected to work fine till 7 hops. Beyond 7 hops the STP will work but it might bit a little hard to predict the behaviour of the STP, which might result in a lots of network problems. From an individual switch perspective like from the root bridge the STP diameter should not be more than 7 hops away.
If you are following Cisco's 3-tier hierarchical design you will never be exceeding the STP diameter.
HTH
Ankur
*Pls rate all helpfull post
07-10-2008 02:11 AM
Hi is there a command to calculate the STP distance? Or must I simply calculate it by hand?
Thx,
Marc
07-10-2008 02:56 AM
IMHO
In bpdu we have max-age which in decreasing from hop to hop by one.
by default max-age is 20
for stability you need that last hop receive bpdu with max-edge not less then 3.
so you can have a chain from 17 switches
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094954.shtml
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