Cisco 2950 and Huawei switch not talking over fibre

Hi all, hope someone can give some advice on here, cos we're stumped. Below is the e-mail that I've been sending to anyone that knows anything about ciscos:

Huawei Quidway S3900 (cheap cisco knockoff). It's a 48 port switch with 4 SFP ports. We have one SFP connector that supplies fibre to a cisco (2950 with two built-in fibre ports) in another building. There is another cisco 2950 in the same cabinet as the Huawei, connected via ethernet. The cisco switch in the other building (connected via Fibre from the Huawei) is connected to two other ciscos in a third building (2950 & a 2900XL) via ethernet. In addition to this, there are seven ciscos and another Huawei connected to the cisco in the first building (access switches only).

The problem we are having is that when we bring the fibre link up, the cisco in the same cabinet as the Huawei becomes inaccessible - even console commands are not accepted. There are no output errors on the switch, it just refuses to do anything and has to be manually rebooted.

At the other end of the fibre link the cisco 2950 accepts console commands and the fibre port shows up and connected, but traffic will not pass between the cisco and the Huawei.

We suspect that some sort of root bridge election is taking place automatically. We noted that one of the cisco switches in the third building was becoming the root bridge. We suspect this is preventing traffic from traversing the fibre link.

The switch that automatically elected itself as "root bridge" was turned off, and at that point, a different cisco switch was incorrectly elected as the root bridge.

When we first tested this scenario, we did get problems with cisco on the end of the fibre connection putting the port into blocking mode because of BPDU's recieved from the Huawei. We set the command "spanning-tree bpdufilter enable" on the problematic port on the cisco, which put the port into a "forwarding" state and allowed traffic to pass briefly, however the root bridge election then kicked in and the traffic stopped.

Hope someone can make sense of this. If necessary I can send a network diagram that will show things a bit more clearly.

Thanks in advance Steve

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Steve Williamson
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