ether channel question

[vinamranfs1]

When we configure ether channels on switches the ports are shown up at layer 1 and layer 2. So how does it prevents formation of loop in ports at physical layer in case if the packet comes back. The  spanning tree thinks it as a single bridge port.

[Peter Paluch]

Hi,

The frame should not come back - that is the trick. If both switches treat the link bundle as a single EtherChannel then every received frame is considered to have arrived through the associated Port-channel interface, not through the physical interface anymore. When the receiving switch decides where to forward the frame further, it can forward it out any other port except the one through which the frame arrived - but because the switch believes the frame arrived through the Port-channel interface, it will never forward it back through any member link of the bundle. This is in fact about pure switching essentials, you do not need STP in any way so far.

Best regards,
Peter

[vinamranfs1]

Thanks peter