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. To solve this problem, forcibly set the interface speed to 100 Mbit/s on both ends or replace the network cable with a Category-5 or higher category cable.