Alcatel OS6850-P48 User Guide - Page 176

Roles Within the Stack Managing OmniSwitch 6850/6850E Series Stacks Pass-Through Mode The pass-through mode is a state in which a switch has attempted to join a stack but has been denied primary, secondary, and idle status. When a switch is in the pass-through mode, its Ethernet are brought down (i.e, they cannot pass traffic). Its stacking cable connections remain fully functional and can pass traffic through to other switches in the stack. In this way, the pass-through mode provides a mechanism to prevent the stack ring from being broken. However, note that when a switch comes up in pass-through mode, it should not be left unresolved. Pass-through mode is essentially an error state that should be corrected immediately by the user. Note. When a switch is in pass-through mode, its information will not display in hardware monitoring commands such as show chassis, show ni, show module, etc. Conditions that can trigger a switch to enter pass-through mode include: • Duplicate slot numbers or incorrect stacking modes have been assigned within the stack • The user has manually forced the switch into pass-through mode using the stack clear slot command Note. If a switch is forced into pass-through mode, the rest of the stack will not be disrupted. Any elements in the stack not operating in pass-through mode continue to operate normally. The most common reason for one or more switches to enter pass-through is duplicate slot number assignments within the stack. So, in order to avoid pass-through mode, it is useful to keep track of the current saved slot numbers on all elements in the stack. Slot number assignments are stored in the boot.slot.cfg file in the /flash directory of each switch. If the stack is booted and the same slot number is discovered on two or more switches, the switch with the lowest MAC address is allowed to come up and operate normally. Meanwhile, switches with the duplicate slot number and a higher MAC address come up in pass-through mode. To check the current slot number stored in each switch's boot.slot.cfg file, use the show stack topology command. For example: -> show stack topology Link A Link A Link B Link B NI Role State Saved Link A Remote Remote Link B Remote Remote Slot State NI Port State NI Port 1 PRIMARY RUNNING 1 UP 3 StackA UP 2 StackA 2 SECONDARY RUNNING 2 UP 1 StackB UP 3 StackB 3 IDLE RUNNING 2 UP 1 StackA UP 2 StackB In this example, note that both slots 2 and 3 have a saved slot value of 2. If this stack is rebooted, a duplicate slot error will occur and the switch with the lower MAC address will be given the secondary management role. The slot with the higher MAC address will be forced into the pass-through mode. page 6-14 OmniSwitch 6850/6850E Series Hardware Users Guide June 2011