How to Design STP Loop Free Network

Posted on 2016-08-13
Last Modified: 2016-08-16
Considering the impact that STP Loop can cause in the Network, I would like to know in real world whether there is granularity in configuration to fend off the loop or just set up VLANs normal way, use the VLAN Interfaces to communicate between VLANs and ignore the granular configuration.

What I mean by granular, to cite just few examples:
- Manually configure for each VLAN a specific Switch to be the Root for that VLAN
- Manually configure Access ports to be Portfast and at the same time configure the Ports with BPDUGUARD
- Manually configure on each VLAN each Blocked port with Loop Guard and UDLD
-Manually configure each VLAN with Root Guad,

if that's the case there should be a Config Template, that encompasses all those concerns.

Any clarifications on that ?

Thank you
Question by:jskfan
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LVL 29

Accepted Solution

Predrag Jovic earned 500 total points
ID: 41754864
Basically that is design question and what are actual needs for specific network.
You can find guidelines for L2 (and other layers) implementation Campus Network for High Availability Design Guide , but details are scattered across the page.

if that's the case there should be a Config Template, that encompasses all those concerns.
Yes. Typically companies create template(s) how specific port type should be configured.
You do not have to use everything that there is there to protect your network, you need to create your own template for that purpose, although those rules are not  enough since in addition there should be general design guide how network should be designed. The reason for that is that you can have different potential problems according to network design.

Author Comment

ID: 41754935
The Example of Network I will use  is a Company that has a Data Center in Site A (the main Site) and has Branches in site B ,C,D,E,F . Each Branch has around 300 computer Users.
Sites are connected with WAN Connection.

All the Servers are in Site A, which means client requests will have to come to Site A to retrieve and Update the Information.
LVL 29

Assisted Solution

by:Predrag Jovic
Predrag Jovic earned 500 total points
ID: 41754992
That actually depends on your network design.
Typically you should have for each location separate VTP domain (with it's own VLANs) and connect main site with branch offices over L3 links. Also typically you will have one VTP server per domain (for that VTP domain) and you can use the same VLAN numbers on for each location.
If you have one VTP domain for all locations it is currently considered as a bad design (L2 end-to-end network). Currently recommendation is to use L3 links wherever it is possible.
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Author Comment

ID: 41755081
Assuming Everything is set up properly..and we are running RPVST.
what do you do next to prevent STP loops ?
Do you have a Configuration Example that you can use on every single VLAN ?

Author Comment

ID: 41755398
Each Site is connected to the DataCenter (Core) as shown below:

Author Comment

ID: 41755399
What Configuration Template will you apply on Access /Distribution/Core Switches in order to avoid STP Loops ?

Author Closing Comment

ID: 41758672
I will do some reading later

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