This is a well known problem. Somewhere in your network is misconfigured. A switch (say Switch A) is configured as trunk port; while the router (say Router B) which connects to Switch A is not. At the same time, Router B is a DLSw peer to the router which connects to Ethernet2 in your diagram. As a result, PVST+ BPDU is transported from Switch A to Ethernet2 Switch by DLSw. When Ethernet2 Switch receives PVST+ BPDUs, it thinks that it is a problem. It blocks the port. Please note that Router B and Switch A may not in the diagram you shown.
One of the easiest solutions is to configure dlsw icannotreach saps aa on the router connecting to Ethernet2 switch. However, DLSw will not transport SNAP frames anymore.
I have written a web page to resolve this problem. The page should be posted to CCO soon. The page contains detailed troubleshooting procedure. Please send me an e-mail to email@example.com if you want me to send you the page. Of course, you are welcome to open a TAC case.
Introduction This article will help you understand the steps on how to
download the UCS licenses from the Cisco Systems website and then
installing it on the UCS. The redacted (blue lines) just covers up
certain numbers for privacy please do not take them...
Introduction This article will help you understand and educate the
customer on how to clear their "expired licenses"
(license-graceperiod-expired) from their UCS-M. If a customer just
purchased a license and needs a step by step guide on how to download
Introduction Prepositioning is a powerful tools on the WAAS platform but
it is not always easy to figure out why your jobs are failing when
trying to retrieve the files.Here is a method that should help you to
figure out the reason why they are not succes...