STP Best setting

[David Kondicz]

Hello,

i just want to ask you what kind of configuration you prefere for situation see on picture?

The routers are connected to Vlan2, the downlink ports are 1gig trunk or acces ports also in vlan 2 but they are protected.

The deep of switches is maximum 5.

The topology is star!

Can you prefere som switch priority? Or leave everything in default?

Thanx

Br

Dave

[Mark Malone]

Hi

The central switch should be the root for STP but that's a bad design as the central switch is also a single point of failure for the whole lan , you should introduce another central switch using glbp or hsrp with the current central switch for better redundancy , set one as spanning-tree root primary and the other stp secondary and dual link them to each access switch , with each switch having a redundant link for failure in case the primary switch failed

[David Kondicz]

Thank you Mark,

the picture shows it in very simple way. The central switch is Cat4506e sup7.

How do you prefere to set interfaces with router connections? Portfast?

My next question is thet i found cat4500e using by default RSTP, but on downlink switches we are using STP only. I have found if i connect  ca cat 2960x on downlink port with STP only, it make an outage on sentral switch Cat4506e. Probably STP uncompatibility?

And is there needed to set up any priority on switches? Or only on central switch?

Thank you

[Mark Malone]

How do you prefere to set interfaces with router connections? Portfast?  As long as its not a trunk portfast is fine

My next question ....... Best to use the same stp mode on all switches when possible , see what they support , spanning-tree mode ? then set them the same on each switch , would need to see setup of ports and logs to confirm its an stp compatibility issue while its occurring. If the port was set as portfast and switch got connected it could disable it also

And is there needed to set up any priority on switches? Or only on central switch?

You can if you want but once you set the primary and secondary on central or core switches its usually enough , all depends on how much control you want over stp

[David Kondicz]

Thanx,

the routers are connected only asi private vlan acces port. That means portfas will be ok?

Ok, it means i need to set up same protokol on all switches = STP, on master switch cat 4500 set as root switch and all other switches will be only as secondary?

This wil prevent also from topology changes that case unicast flood?

Thanx

dave

[Mark Malone]

as long as the router side is ip and not a switching module its fine for portfast

yes set 4500 as root for STP and then pick another switch centrally located as the secondary then leave the rest as default

unicast flooding can occur many different ways in stp but having control over your topology will help restrict that from happening, the more time you put into setting up the config and ports for STP the quicker the convergence will be when there is an issue

[David Kondicz]

thank you,

i try it and let you know... i need to decrase any topology changes on central cat 4500e becouse we have loaded here aroud 10 000 macs and while we have topology change on this swith, the mac numbers falling to 1500...

thanx

dave

[Joseph W. Doherty]

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BTW, on later Cisco switch's IOSs, you can make port fast (and BPDU guard - which you often want to use with port fast) as edge port defaults.

[David Kondicz]

Mark, isnt there a better way to use port setting like this:

Link-Type point-to-point: Links between switches

Edge-Type point-to-point: Link between switch/end user

Link-Type Shared: Link between switch and a hub

than setting up as portfast?

Thanky you

Br

Dave

[Mark Malone · Accepted solution]

Edge-Type point-to-point: this is portfast , any pcs, printers ,phones etc directly connected devices you want removed from STP calculation when a TCN change occurs , to speed up convergence at L2

if its connections between switches you can use trunk or access depending if there's multiple vlans doesn't really matter , just don't use portfast on a trunk link ever unless its a switch to a SAN server , never between switches

if you have a HUB on your network I would remove it

portfast is to be used in edge devices and in combination with bdpuguard  for best practices as per Cisco