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Trouble with Link Aggregation

Trouble with Link Aggregation

Trouble with Link Aggregation


I am new at this forum and - of course - i have a problem.
Hopefully one of you is having an idea or hint to solve it.

I have two 3Com Switches - 4050 connected together with XRN modules.
This both switches are at 4th floor.
My server Room is at 3 floors lower.
At this there are two 3Com 500G Switches. They are stacked too. The Problem is:
There is one link aggregation from Core Switch - 4050 (member 1) to 1st Member of 5500 Stack. Both cables are LWL.
This link aggregation is working properly.
Because there is no redundancy to the Server room (if one of this both switches fails) my employer asked me to solve this problem.
The guy before me tryed to add 2 links from the second core switch to the 2nd member of the stacked swítch at server room. It didn´t work - this was told to me.
By mischanche i had only a very short while to ask...
At last Friday evening i added 2 Ports to the link aggregation group (same group)- and all ports were showed as up. All was looking fine.
After removing the port from Core Switch 1 - all was locking fine too...telnet sessin was working to the switches at server room - i lost only some ping packets.
But: PC´s were not able to log on at their domain and Internet was not working too.

At this site: All is in one big VLAN (i know this is bad, but please note - i am there since 2 Weeks - i am a new employee there.)
All in one - at the moment i have no idea what the reason can be for this.
Normaly - if the master port of Link aggregation - the next will take mastzer role and so on.
After removing the two additional ports - all was working properly again,

Do you have any idea what the problem could be ?
(And yes - i was thinking about STP)

best regards


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