<div>
Provide your configuration please?
</div>


<div>
What you mean by trunk ? Is this a dot1q trunk or just an access port on the VLAN? Is Spanning Tree enabled on the VLAN you are using ?<br />

</div>


<div>
I with donboo ; but please provide config of sw.'s in both ends of link if you still have prob.'s.<br />
Also: first config then connect. 
</div>


<div>
<div class="content wysiwyg-content">
I have two new HP2824 Procurve Switches, I setup a Trunk on Ports 20 and 21 from the CLI. &nbsp;When I connect a cable to the rest of the network, a loop back condition happens on the network. &nbsp;All of the clients start dropping network connections and the entire network goes down. &nbsp;Does anyone what I have done wrong setting up the Trunk? &nbsp;Everything is in VLAN0
</div>
</div>


I have two new HP2824 Procurve Switches, I setup a Trunk on Ports 20 and 21 from the CLI.  When I connect a cable to the rest of the network, a loop back condition happens on the network.  All of the clients start dropping network connections and the entire network goes down.  Does anyone what I have done wrong setting up the Trunk?  Everything is in VLAN0

HP Switch Trunking Causes Loop-back on network

A switch is a device that filters and forwards packets of data between LAN segments. Switches operate at the data link layer or the network layer of the Open Systems Interconnection (OSI) Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. A hub is a connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports; when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.