Trunk with Etherchannel

Hello all,

I have an environment with two switchs, Dell and Cisco, and one firewall, I put the firewall as a bridge with etherchannel and trunk, and different Vlans on each side, it looks like this:

Host_1.1.1.1/24                                                                           Host_1.1.1.1/24

   | V100                                                                                                     | V101

Cisco    --Ether_Trunk_V100->   FW     --Ether_Trunk_V101->   Dell

On the Dell SW side, I see that STP disables these ports, even if i do "spanning tree disable" command, it still doesn't work. if I replace the Dell with another Cisco SW with the same configuration it works fine.

Do you have an idea what can cause this?

Thanks.