In V100R006SPC800 and later versions, switch interfaces cannot work at a lower speed through auto-negotiation by default. If two GE interfaces are connected using a 100M network cable (Category-5 or lower category cable), the interface speed cannot be negotiated as 100 Mbit/s and the two interfaces are in Down state. You can manually set the speed of the two interfaces to 100 Mbit/s or replace the 100M network cable with a 1000M cable.