There are a number of timer based steps in spanning-tree with 802.1d, basically the 20 second timer is for max-age, which is like a hold time for a specific port, if a switch receives bpdu's (spanning-tree packets) from a port, then that packet is valid for 20 seconds, if none are received within 20 seconds, then the switch starts to go thru convergence to select a new port.
You can tune the timers for 802.1d, but this can have an adverse effect on the network due to constant topology changes etc, if you are looking for fast convergence then you should look at switching to 802.1w, rapid spanning-tree.
- 20 second to age out some information. This generally does not happen in a modern network with point to point links. When a link goes down, each end detects the failure and the associated information is aged out immediately.
- 30 seconds to move a port from blocking to forwarding. This is with regular STP. Portfast and uplinkfast were already enhancing the convergence for most of the case. With RSTP and MST, in a correctly configured network with p2p links, you should be able to move a port from blocking to fowarding with no timer intervention.
So the 50 seconds that is still advertised everywhere is really a worse case scenario, most relevant to an older version of the standard (STP has been deprecated by RSTP: 802.1D *is* RSTP now!)
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
Im studying the 100-105 book by Odom and am currently on the topic of Port security. I purchased a used 2960 and I'm trying to follow a...
While deploying a number of 18xx/2802/3802 model access points (APs), which run AP-COS as their operating platform. It can be observed on some occasions that while many of their access points were able to join the fabric WLC withou...
I am going to design and build an LAN network under a tunnel underground with long distance between the switches.
I will have 2 Catalyst switches and 8 Industrial IE3000, and they will be connected with fiber.
For now I am planning on use Layer-2 s...