I have three Cat3500XL switches and four gigastack modules available. I am currently using only three with one cable between each switch. The default mode on these ports seems to be half duplex and the ports will settle into that mode. I have tried reconfiguring the speed to 1000 and duplex to full but they won't settle into that mode. Port negotiation never stops. The second issue I cannot resolve is redundancy in a loop configuration (Connecting SW1 to SW2 and SW2 to SW3 and then SW3 back to SW1). Spantree just won't resolve it. CatOS is 12.0(5.3)WC(1)
Yes GBICs do run full duplex. I am running a 1 gig fibre link between buildings (Multimode Fibre). This provides the link to the other 3548. (48 port switches with 2 gbics). So far no problems. I check the stats on the switches every week so far no problems and no real errors.
The gigastack modules I am using are two port copper modules used to stack the switches not the fiber or 1000BaseT modules. They use a propriatary link cable that looks like RJ45. The port can be reconfigured by turning off autonegotiate and setting the speed and duplex. They go green but then start flashing orange within seconds.
Drew, in my experience (I have 3524's and 3548's with GigaStack GBICs), they will only run full duplex if there is only one cable attached to it. If both ports on the GBIC are used, it runs half, and the other end of the link runs half. So, if you want to run full duplex, use one port on it only, leave the other port empty. Hope that helps!
Some people before already told you that full duplex only will work with just 1 cable connected between 2 switches. If you connect more switches it wil be seen as a bus and opperate in half duplex mode.
For the oher issue the loop back for redundancy, we are using it with succes. We are running 12.0(5.2)XU.
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