FlexLink issue

Unanswered Question
Jul 10th, 2008

Hello


I am testing the flex link feature on 3750 and 3560 switches in my lab. I found the following problem:


When the primary link is going down on the access switch it takes one second to switch to standby link. But if after the switchover I remove the cable from the current active port in 30 seconds the traffic is stopped. I measure it with the stopwatch and it seems that after the first switchover the standby port could not be back active (could not forward traffic) for maximum 30 second. After this time there is no problem with the switchover.


Does anybody know what is the reason for such behavior and if I can fix it somehow?


Just to make it clear I have already try to configure the mac-address move feature but it does not help. I have also try to configure the portfast on the links that are working as flex links but this also does not help either.


Thank you in advance


Lukasz


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n.nandrekar Fri, 07/11/2008 - 00:12

hi!

During the timeperiod when the link is not forwarding the traffic (i.e. for the 30 sec) can you check the status of "sh spanning tree" (or "sh spanning tree vlan x" if you are running pvst) ? Does it show the flexlink port in listening/learning state? then it could be expected behavior due to convergence. You would need to make sure that that stp is disabled on the ports, or if you have configured portfast, make sure that you also configure bpdu filtering on the ports so that bpdus are not sent on the port and there is no convergence triggered.

A portfast link would lose its portfast status if it recieves a bpdu on that port. You also have to make sure that you configure this on both the sides and then bring up the link.


Regards,

Niranjan

(pls rate if helpful)

lukaszkhalil Fri, 07/11/2008 - 00:27

Hello


By default when the flex link is configured the STP should be turned off on those ports. When I configure the flex link feature those to ports (active and backup) disapper from the spanning-tree output.


I am using rapid-pvst.

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