[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

STP and Timers

Posted on 2011-02-12
7
Medium Priority
?
855 Views
Last Modified: 2012-05-11
any expert out there to explain the relation between STP and the timers used in STP:

for example:

Hello Time
Max Age
Forward Delay
-------------
Blocking
Listening
Learning
Forwarding

Thanks

0
Comment
Question by:jskfan
7 Comments
 
LVL 17

Accepted Solution

by:
surbabu140977 earned 668 total points
ID: 34878978
hello time is 2 seconds
The Max Age Timer is 10x the the hello timer.
STP has 4 states: blocking, listening, learning and then forwarding
Once a port is in blocking state, it stays there for 20 seconds. Then moves onto listening at 15 seconds, then learning at 15 seconds. That's where you get your 50 seconds

RSTP
------
The max age is 3x the hello. So a max of 6 seconds. There's no blocking port in RSTP. It's discarding state. Discarding replaces blocking and listening. So you only have discarding, learning and forwarding.

forward_delay = ((4 x hello) + (3 x dia)) / 2
the Forward Delay Timer specifies the time a port stays in each of the listening and learning states

Example from cisco site,

hello = 2 (default) then
max_age = 14 sec
forward_delay = 10 sec
If hello = 1 then
max_age = 10 sec
forward_delay = 8 sec

Best,
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 34879557
Can you elaborate as to what it is that you want to know?
0
 

Author Comment

by:jskfan
ID: 34882486
I wanted to know how they are related, for instance if there is change in Hello time, Max age and Forward Delay, how it is going to impact the blocking ,listening,learning, forwarding operations
0
[Webinar] Cloud and Mobile-First Strategy

Maybe you’ve fully adopted the cloud since the beginning. Or maybe you started with on-prem resources but are pursuing a “cloud and mobile first” strategy. Getting to that end state has its challenges. Discover how to build out a 100% cloud and mobile IT strategy in this webinar.

 
LVL 8

Assisted Solution

by:SeeMeShakinMyHead
SeeMeShakinMyHead earned 668 total points
ID: 34882569
I would read this article as it explains it all.  If you are using spanning-tree instead of routed links, then I would use RSTP as it is much faster.  There are some sites where I have to use STP and I use RSTP since recovery on failed links it quite a bit faster.  So fast, that users really couldn't tell.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094954.shtml
0
 

Author Comment

by:jskfan
ID: 34889795
After reading, I noticed that Hello,Max age, Forward Delay are pretty much other names used for blocking, listening, learning , forwarding.

Hello (02)+ Max Age (20) =  they can be mapped to Blocking state
Forward Delay= Can be mapped to Listening(15) + Learning(15)

the only difference is on the switch there are commands that can change  the Hello, Max age, Forward delay timers
but no command that can change  Blocking ,listening, learning, forwarding
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 664 total points
ID: 34889899
Blocking, listening and learning are port states that are the RESULT of timer values.

If, for example, you wanted a failure to be detected quicker, you could lower the Max Age timer. And if you wanted to reduce the amount of time spent in listening/learning, you could reduce the Forward Delay timer. But tweaking timers can be problematic if you aren't careful.

For example, in almost 20 years of working with Spanning Tree, I have never altered the timers in a production network.
0
 

Author Closing Comment

by:jskfan
ID: 34890136
thank you guys!
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The worst thing when starting a new job is when the previous Network Administrator left behind no documentation. How do you get into the devices? If you've been in this situation or just accidently mistyped your password, this article will hopefully…
I eventually solved a perplexing problem setting up telnet for a new switch.  I installed a new Cisco WS-03560X-24P switch connected to an existing Cisco 4506 running a WS-X4013-10GE Sup II-Plus. After configuring vlans and trunking,  I could no…
When cloud platforms entered the scene, users and companies jumped on board to take advantage of the many benefits, like the ability to work and connect with company information from various locations. What many didn't foresee was the increased risk…
As many of you are aware about Scanpst.exe utility which is owned by Microsoft itself to repair inaccessible or damaged PST files, but the question is do you really think Scanpst.exe is capable to repair all sorts of PST related corruption issues?

872 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question