Connect the Cisco Catalyst 3524 to an existing network connected by a switch. The main switch is a Catalyst6509, and its GBIC is already connected to the Catalyst4006 switch. I decided to use the port of the Catalyst 6509 module 3 and use a Type 5 adapter cable to connect the fast Ethernet ports, namely the 3/15 port of the Catalyst 6509 and the 0/1 port of the Catalyst 3524. En même temps, set the two ports to 100Mbps, full duplex, the same VLAN1 administrative domain and the same VTP domain and the same VTP mode (server mode). The backbone mode and packaging of the two ports are set to non-negotiated and 802.2q respectively. So there is a problem: when I ping any IP address from the Catalyst 3524 console on the network, although I get a successful rate of 0/5 port, there is no data transfer between the two switches. I suspect that the Catalyst 3524 Ethernet port does not have backbone capability, so I did a port display on the Catalyst 3524 console, but I did not get