HUBO HUBI HUB2 HUB HUB4 高一级HUB uplink Portl Port2 Port3 Port 低一级HUB uplink Portl Port2 Port3 Port PCI PC2 PC3 PC4 HUB级联模型图低一级 HUB uplink Port1 Port2 Port3 Port4 高一级 HUB uplink Port1 Port2 Port3 Port4 PC1 PC2 PC3 PC4 HUB 级联模型图 HUB0 HUB1 HUB2 HUB3 HUB4 PC PC