in my home lab environment I have 2 2924XL switchs, 1 2950, 1 2960 and 1 3550.
They are all connected to each other via redundant links.
All links are 100Mb
All the switches use the same priority.
I documented all the MAC addresses of each switch using "sh ver"
I then using my limited knowledge of STP presumed to know which ports were blocking, forwarding and root and documented this.
Bearing in mind the above setup...
I know that the root bridge is the lowest BID
I know that the root ports are closest to the root bridge,
I know that the Designated ports are chosen on the switch with lowest BID
Blocked ports are chosen on the switch with the highest BID.
Now when I verify this I conclude that a 2924 which has the highest BID of all my switches will have some blocked ports (depending on how they link together). What I find however is that the switches connected to this 2924 which have lower BID have blocked their ports, and the 2924 has all forwarding.
The 2924 is not the root bridge.
I cannot find why this is happening, is this possibly a bug with older switches? Do you need more info?
any help would be greatly received
Have you set the spanning-tree priority manually?
Old switches used to have a 16 bit bridge priority vlaue. The new switches use the extended system ID and the bridge priority is a 4 bit value
Since 2924 is selected as the root switch, it will have its port in the forwarding state.