3048, vlans Spaningtree Cisco switchs not forwarding

Hi,

We have a site with a Dell 3048 running approx 35 Vlans

Hardware Version:   PC-3048-00 
Boot ROM Version:   4.5.2172 
Software Version:   6.1.2.3291 

There are a number of Layer 2 switches hanging off ethernet ports that are VLAN marked as Untagged.  The makes of these switches are HP, Netgear, DLink, Baynetworks, 3Com, Cabletron ( fair industry spread!!)

The Giga uplink port is connected to a Cisco 3550 Layer3 switch & onwards to routers, the internet etc etc.

 

The principle is that different PCs(via 3rd party switches/hubs) are connected to different VLANS, These VLANS are presented as VLAN subinterfaces & routed on the Cisco 3550 & passed to the Internet, thus providing seperation & internet access to the VLANS

Ie the Dell acts as an accumulator/aggregator bringing multiple seperate switchs together via VLANS & presenting to the Cisco 3550 to handle the inter-vlan routing & forwarding

This all works fine ..... as long as none of the client switches is a Cisco!!

If we plug a cisco switch (Ill refer to these as client ciscos) into a non-vlan-trunk ( not to be confused with a trunk port) that is not the Default VLAN, (ie any VLAN id > 1) the cisco pops up the following on the client cisco

Switch#sh spant
%LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
%SPANTREE-2-RECV_1Q_NON_TRUNK:
Received 802.1Q BPDU on non trunk FastEthernet0/1 on vlan 1.
%SPANTREE-2-BLOCK_PORT_TYPE: Blocking FastEthernet0/1 on vlan 1.
Inconsistent port type.
%SPANTREE-2-BLOCK_PVID_LOCAL: Blocking FastEthernet0/1 on vlan 1.
Inconsistent local vlan.

a SHOW SPANTREE

gives the following
Interface Fa0/1 (port 13) in Spanning tree 1 is BROKEN (PVID & Port type)
   Port path cost 19, Port priority 128
   Designated root has priority 24577, address 000e.8368.5580
   Designated bridge has priority 32768, address 0030.ab23.2f30
   Designated port is 43, path cost 4
   Timers: message age 2, forward delay 14, hold 0
   BPDU: sent 2, received 6

Debuging/workarounds tried to date

• I have tried 4 different Cisco Switches as clients ( 4006, 2900, 2550, 2900XL) with different versions of software.
• Connect the client Cisco switches directly to the Cisco 3550 All works fine.
• Connect the Client switches to the network through one of the existing third party switches, the Cisco still drops out but the third party switch keeps working.
• Disconnect Dell 3048 from the cisco 3550 & the client cisco goes back forwarding ( but the network is broken)
• Disabled all interfaces on Dell except the uplink & single port to Client cisco & same.
• Upgraded the Firmware on Dell to latest on website.
• We have swoped out the Cisco 3550 Switch.  Disabled all interfaces bar the uplinks.
• Changed the root Spantree to the 3550

The bottom line is that it appears to be an incompatability between the Dell & the Cisco  3550 .  If I change the VLAN on Dell port connecting to the client cisco to a VLAN 1 all works fine but any other VLAN on the Dell & out it goes.

I have a CCIE looking from the Cisco side but where is no joy there.

This is a very heavly used production system & resets & tests etc take lots of scheduling.

Any direction would be welcomed.