interfacing dell S4128F switch with ATGS950/24 allied telesys switch

Hello,

i summit a problem concerning the connection of S4128F switch with an allied telesys ATGS950.  

the connection is physically done with a sfp+/RJ45 at 1GBPS on S4128 and RJ45 connection on the ATGS950

my dell configuration is very simple   juste the vlan 1 by default + rstp + switchport acces on all interface.   i'm not responsible of atgs configuration but i know That nothing has been configured.    

when i start the dell switch nothing is pingable on the atgs network from the dell switch  only the ip managent adress is pingable. 

it works only if i disable the switchport  (no switchport) and reenable (switchport mode access)

but i restart i have to remake the same commmand 

i will be very pleased if someone could help me.  th dell support was not able to help me