Table of Contents
Advertisement
Managing OmniSwitch 6450 Stacks
Basic Operation
When stack split detection is enabled, a proprietary protocol runs on a configured link aggregate to carry
the stack information necessary for stack split detection. Stack elements share a link aggregate with an
OmniSwitch that can act as a helper to assist in the stack split detection.
The lowest member port of the link aggregate hosted on the primary element is responsible for sending the
SSP PDUs on the member link. When the packet arrives on the remote helper device then the helper
device will forward the packet out on all member ports of the link aggregate so that the packet reaches the
remote stack elements.
Use the the
stack split-protection
create the SSP link aggregate on the stack.
Use the the
stack split-protection helper
the SSP helper and create the SSP helper link aggregate on the helper switch.
Protection States
Under normal stack circumstances the SSP PDUs are sent once every 3 seconds. When the stack detects a
scenario which leads to a change in its size the protocol sends the SSP PDUs at a rate of 1 per 250 milli-
seconds for 120 seconds. This helps to quickly identify a stack split.
On reception of a SSP frame, the receiving elements match the primary of their current stack against the
MAC address of the SSP sender. If there is a mismatch between the two, then that indicates the presence
of an active stack in the network which is disconnected from the current stack. In this condition the stack
element will monitor 3-5 such consecutive frames, after which it will transition to the protection state.
When an element transitions to the protection state, the following occurs:
Each of the stack elements will independently transition into the protection state.
•
•
In the protection state each of the stack elements will disable all the user ports except the ones belong-
ing to the SSP protection link aggregate.
•
The stack element will store the protection state transition information in a non-volatile location
(EEPROM/ boot.params). This information will be used whenever an element in the protection state
re-boots and needs to check its current operational state.
•
An element in the protection state will send an SSP PDU back on the link aggregate carrying the SSP
state as PROTECTION. This is the only frame that is sent by the protection sub-stack. The purpose of
this message is to inform the active-stack to generate an SNMP trap regarding the stack split state of
the stack element.
Stack Split Recovery
Once a sub-stack goes into the protection state then all the front panel ports are put into an operationally
down state. There are two ways to recover the stack, manually or automatically.
Manual Recovery:
If the guard timer is 0, automatic recovery is disabled and the sub-stack stays in protection mode until the
unit is reloaded by the administrator. After the re-boot the administrator has to manually recover the
switch by first disabling SSP and then re-enabling SSP. This clears the protection state variables stored in
the EEPROM/boot.params.
OmniSwitch 6450 Hardware Users Guide
and
stack split-protection linkaggid
and
stack split-protection helper linkagg
September 2015
Stack Split Detection (SSP)
commands to enable SSP and
commands to enable
page 7-39
Hide quick links:
Advertisement
Table of Contents
