Issue: ====== Replaced the faulty switch with the new one after which I see the port was shown down. europe3750#sh switch detail Switch/Stack Mac Address : bbde.4B9H.5690 H/W Current Switch# Role Mac Address Priority Version State ---------------------------------------------------------- 1 Member 7012.cH5h.dn00 1 1 Ready *2 Master bbde.4B9H.5690 15 1 Ready europe3750# Show switch stack-port Stack Port Status Neighbors Switch# Port 1 Port 2 Port 1 Port 2 -------------------------------------------------------- 1 Down Ok None 2 >>>>>>> Port showing down. 2 Ok Down 1 None Hence Troubleshooting done: ========================= Replacing the stack cable. >> No issues as this stack cable working fine. Resolved after rebooting the switch. ======== Tried reseating the stack cable Stack Port Status Neighbors Switch# Port 1 Port 2 Port 1 Port 2 -------------------------------------------------------- 1 Ok Ok 2 2 2 Ok Ok 1 1 == Question: ============= Why did reboot resolved the issue? Is there any communication error when we connect the stack cable between the switches? Does it always required to reboot the issue connecting the switches in stacking? If yes can you please guide me the communication happening between each other?