Solved

Loop Guard

Posted on 2015-02-24
9
82 Views
Last Modified: 2015-02-25
An article about Loop Guard and I want to clarify my understanding

Loop guards : The switch figures out which ports are nondesignated and monitors the BPDU activity to keep them nodesignated. Nodesignated ports are generally the root port, alternate root ports and ports that normally are blocking.

BDPU is forward by Designated Port and received by Root Port on another switch.  Why does it say root port is blocking ?

Do I misunderstand something ? Tks
0
Comment
Question by:AXISHK
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 4
9 Comments
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40628087
The switch figures out which ports are nondesignated and monitors the BPDU activity to keep them nodesignated.
This is correct.
Nodesignated ports are generally the root port, alternate root ports and ports that normally are blocking.
No.  nondesignated ports are any ports which received inferior BPDU's (BPDU's that have a higher cost than the preferred BPDU). "Blocking" is another way of saying "nondesignated".
BDPU is forward by Designated Port and received by Root Port on another switch.
This is correct.

But none of what you've said is really related to loopguard.  So I'm not sure what it is you're misunderstanding.
0
 

Author Comment

by:AXISHK
ID: 40628192
The original message is
" You can enable loop guard on all switch ports, regardless of their functions. The switch figures out which ports are nondesignated and monitors the BPDU activity to keep them nodesignated. Nodesignated ports are generally the root port, alternate root ports and ports that normally are blocking."

Nodesignated ports are generally the root port, alternate root ports and ports that normally are blocking.

Is Root port blocked ? Base on my understanding, "Block" means that the port can receive BPDU but can't forward it out, or other frame, correct ? Tks
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40628205
Can you post a link to the article?  

Is Root port blocked ?
No. Root ports are never blocked. If they were, they wouldn't be root ports.

Base on my understanding, "Block" means that the port can receive BPDU but can't forward it out, or other frame, correct ?
This is correct.
0
Portable, direct connect server access

The ATEN CV211 connects a laptop directly to any server allowing you instant access to perform data maintenance and local operations, for quick troubleshooting, updating, service and repair.

 

Author Comment

by:AXISHK
ID: 40629788
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40629849
Yeah, that's the standard Cisco document on loop guard. Sometimes I think they write that stuff to intentionally confuse people.
0
 

Author Comment

by:AXISHK
ID: 40629870
just to clarify

Root port can only receive BPDU but it can't forward BPDU and frame. In fact the port does not block but Cisco just interrupt it as "blocked" in a the sense that root port doesn't forward any packet, correct ?

Tks again.
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40630306
No. The root port receives and processes BPDU's, and data frames.  It also sends data frames.

A root port is classified as a forwarding port.
0
 

Author Comment

by:AXISHK
ID: 40632234
Tks, so root port receives and processes BPDU but it do not forward BPDU, BDPU should be forward out by Designated port, correct ?
0
 
LVL 50

Accepted Solution

by:
Don Johnston earned 500 total points
ID: 40632294
Correct.
0

Featured Post

Free NetCrunch network monitor licenses!

Only on Experts-Exchange: Sign-up for a free-trial and we'll send you your permanent license!

Here is what you get: 30 Nodes | Unlimited Sensors | No Time Restrictions | Absolutely FREE!

Act now. This offer ends July 14, 2017.

Question has a verified solution.

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

Meet the world's only “Transparent Cloud™” from Superb Internet Corporation. Now, you can experience firsthand a cloud platform that consistently outperforms Amazon Web Services (AWS), IBM’s Softlayer, and Microsoft’s Azure when it comes to CPU and …
This article is a collection of issues that people face from time to time and possible solutions to those issues. I hope you enjoy reading it.
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …
Monitoring a network: why having a policy is the best policy? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the enormous benefits of having a policy-based approach when monitoring medium and large networks. Software utilized in this v…

696 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