PE Ring FSM States

There are four Finite State Machine (FSM) states for a PE ring:

  • INIT: The PE chains are in the Init state when there is no PE ring in the setup. 

    ICX7750-48F Router# show spx ring all

  ------------------------------------------------------------------------------------
  Ring Id |FSM State |CB port  Lag  |Remote CB port  Lag  |Log Block Link
  ------------------------------------------------------------------------------------

ICX7750-48F Router# show spx ring chain

  ----------------------------------------------------------------------------------------------
                             SPX CB [CASC PORT] CHAINS                       
                                                                      
  CB Port    Lag  | Epoch |Ring    Id      FSM State|Remote CB port  Lag  |         Chain           
  ----------------------------------------------------------------------------------------------
  2/1/9      3075  126     NO      0       INIT      INVALID         0      PE22--PE21
  1/1/5      3079  126     NO      0       INIT      INVALID         0      PE17--PE18--PE19--PE20

  • IN_PROGRESS: The PE ring is in the In Progress state when it transitions from Break to Active or vice versa.

  • ACTIVE: Once the PE ring is formed, the FSM state changes to Active. 

    ICX7750-48F Router# show spx ring all
  ------------------------------------------------------------------------------------
  Ring Id |FSM State |CB port  Lag  |Remote CB port  Lag  |Log Block Link
  ------------------------------------------------------------------------------------
  1        ACTIVE     1/1/5    3079  2/1/9           3075   PE20x--xPE21

  • BREAK: The PE ring is in the Break state when the CB-PE or PE-PE SPX link is broken or when a PE unit or a CB unit fails. For an SPX LAG, the PE ring state moves to Break only when all links in the LAG go down.

In an existing SPX setup, a PE ring can be formed in two ways: 

ICX7750-48F Router# show interface brief ethernet 20/1/1 ethernet 21/1/1

Port       Link    State   Dupl Speed Trunk Tag Pvid Pri MAC             Name
20/1/1     Down    None    None None  None  No  1    0   cc4e.248b.11e0                 
21/1/1     Down    None    None None  None  No  1    0   cc4e.24b4.7f20                 

ICX7750-48F Router# show spx ring all

  ------------------------------------------------------------------------------------
  Ring Id |FSM State |CB port  Lag  |Remote CB port  Lag  |Log Block Link
  ------------------------------------------------------------------------------------
  1        BREAK      1/1/5    3079  2/1/9           3075   Ring is broken - No Logical Block

  • Connect the edge PE to the CB.

  • Connect the edge PE in a chain to the edge PE of another chain.

Restrictions on Forming a PE Ring

  • You cannot form a ring by connecting a PE to another PE in the same chain.

  • A maximum of six PEs is allowed in a PE ring.

  • A new PE ring within an existing PE ring is not allowed.