STP and UDLD doubt

[K.Prashant Rao]

Hello All,

 

Manish and I came across a situation at work with STP loop and hence had to go back to Cisco website to read/refresh STP concepts.

 

We  happened to come across this link

 

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009477b.shtml

 

Need your assistance to help me understand a point there.

 

In the very beginning of that doucment, there is a small topology with 3 switches running STP.

 

When i read thru it, I couldnt really comprehend the following statement

 

Now, consider what happens if the link B-C fails in the direction of C. C stops receiving traffic from B, however, B still receives traffic from C.

 

Please could you helo me understand, why they are saying what they are actully saying there ?

 

I mean, if the link between B and C fails in the direction of C, C would stop recieving packets from B, thats fine but  then how can B keep recieving packets from C ?

Think I am forgetting something here or not able to understand the statement, the way I am supposed to

 

Thank you.

--
Prashant K Rao
also goes by "Peru"

[rafatur rahman]

Hello,
Please refer to this article: http://rafaturrahman.blogspot.com/2009/08/udld-behaviour.html

do let me know if this clarifies the doubt or any further summary is needed.

Thanks
Rafatur rahman

[K.Prashant Rao]

Hello,

 

Yes, this clarified my doubt. I didnt think in terms of Rx and Tx Fiber connections. Thats where I missed the ball.

Thanks a lot for looking into this for me.

 

Prashant.

I have learned whatever state I am in,
to be content ~Phil 4:11

[Fahad Rahmani]

Hello,

This is also available for copper but primarily this was for fiber optic connections.. Now, we have solution within STP.. spanning-tree guard loop // will do the same job..

Keep an eye on Flex links, as an alternative or similar technology to STP... other similar technology form HP Procurve is mesh and new but very encouraging is VSS for high end switches from Cisco. There is another new very interesting feature added by ProCurve recently is for detection of loops beyond your access link.. "this is new to my knowledge" and addresses something which was called for from years.. we will discuss that very soon...

I think a write up is called on L2 designs.

Rafatur could you kindly do a technology walk on Flex, including cam population, preemption, loadbalancing in this context please...

Regards.

--
Fahad Rahmani
+91 9740 755 800