Cisco Systems SLM224G4PS 사용자 설명서

If the incoming unit already has an assigned Unit ID, 

and that Unit ID is unused in the current stack, the 

incoming unit will keep its assigned Unit ID and the 

Master will apply to it any configuration relevant to 

that Unit ID. 
If the incoming unit already has an assigned Unit 

ID, and that Unit ID conflicts with a unit ID in the 

current stack, the Master will reallocate a new 

Unit ID to the incoming unit, giving it the lowest 

available Unit ID (assuming, of course, that the 

incoming unit does not have a manually assigned 

Unit ID, which the Master cannot change).
If the incoming unit cannot be assigned an 

available Unit ID for any reason (in the case of unit 

replacement that can only happen if the incoming 

unit has a manually assigned Unit ID), then it will be 

effectively shut down—that is, it will not be joined 

to the stack. 

The  stack  Master  will  now  carry  out  Unit  and  port 

configuration for the incoming unit.

Any configuration information the Master has that 

is relevant to the number assigned to the incoming 

unit will be applied. In particular, if the incoming 

unit was assigned the same Unit ID of the unit it 

replaces, then it will receive the same configuration 

as the failed unit, to the extent possible, as 

described in section “Replacing a Failed Stack 

Member in a Running Stack“ above. 

In  this  example,  let  us  assume  that  a  working  stack  is 

split into two groups, either by failure of a stacking link 

connecting two units in the stack or by a failed unit in a 

chain topology which causes disconnection between two 

units  in  the  stack.  In  this  case  we  should  consider  each 

subgroup as an independent running stack configuration. 

For each subgroup three suboptions will be considered:

Both the Master unit and the Backup master unit are 

part of the subgroup.
Either the Master unit or the Backup master unit are 

part of the subgroup.
Neither the Master unit nor the Backup Master unit are 

part of the subgroup.

The  following  describes  what  happens  within  each 

subgroup for each of these three suboptions.

Nothing changes, except the master sees the missing 

units  as  having  been  removed,  and  routes  traffic 

around  them,  as  described  in  section  “Replacing  a 

Failed Stack Member in a Running Stack” above.

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Since this subgroup contains both master and backup, 

the subgroup works, and the other subgroup will not 

work. Refer to step 3 below for detailed information.
The sequence of actions is as follows:

The Master Discovery, Master Election and Unit ID 

Allocation & Duplicate Unit ID Conflict Resolution 

processes will be executed.
Any  configuration  information  that  the  Master 

has  that  is  relevant  to  the  units  remaining  in  the 

subgroup will remain unchanged. 
Topology  information  (the  information  for  each 

unit on how to send traffic to any other unit in the 

stack)  managed  by  the  master  will  include  only 

units that are reachable (connected) following the 

split. 
The subgroup continues to work as before, except 

that the number of the unit is lower than prior to 

the split.
No unit ID changes are made in either subgroup.
The Master notifies the system administrator (using 

SYSLOG messages and SNMP traps) of the removed 

units and ports which belong to the unreachable 

units and will be reported as ‘not present’.

If  the  Master  unit  remains  in  this  subgroup, 

this  is  the  same  as  described  in  section  

“Replacing  a  Failed  Stack  Member  in  a  Running 

Stack”  above.  If  the  Backup  Master  unit  remains  in 

this subgroup, then this is the same as section “Stack 

Master Failure and Replacement” above. 
It should be emphasized that if the stack is split into 

two  parts,  one  with  the  master  and  one  with  the 

backup, both parts will work.
The sequence of actions is as follows:

The Master Discovery, Master Election and Unit ID 

Allocation & Duplicate Unit ID Conflict Resolution 

processes will be executed.
If  the  subgroup  contains  the  Master  unit,  the 

stack  Master  notices  (using  the  master  detection 

process)  that  some  units  no  longer  respond.  At 

the same time the stack Master notifies the system 

administrator (using SYSLOG messages and SNMP 

traps) of the removed units and ports which belong 

to  the  unreachable  units  and  will  be  reported  as 

‘not present’.
If the subgroup contains the Backup Master unit, 

the  Backup  Master  will  see  as  a  case  of  Master 

failure  and  take  over  and  manage  the  remaining 

units as a stack, while keeping its number as it was 

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a.

b.

c.