Manual Switch

In the absence of a failure, an operator-initiated Manual Switch (MS) moves the blocking role of the RPL by blocking a different ring link and initiates the node sending a R-APS (MS) to inform the RPL owner to unblock the RPL. This can occur if no higher priority request exists in the ring.

Consider a ring consisting of nodes ERN1, ERN2, ERN3, and ERN4. Dual-end blocking is enabled between ERN1 and ERN2.

A node that receives the R-APS (MS) forwards it to the adjacent nodes. If the receiving node is already in the Idle or Pending state, it unblocks the non-failed port and stops transmitting R-APS messages. Only one MS can exist in the topology at any time. An MS condition has to be manually cleared.

Note

Note

If any ERN is in an FS state or in a protected state through an SF event and an operator tries to configure an MS, the ERN will reject the request.

When a manual switch is cleared by an operator on the same node on which the MS is configured, the node keeps the port in a blocking state, sends out a R-APS (NR) to the adjacent node, and starts the guard timer. Other nodes that receive the R-APS (NR) forward the message. When the RPL owner receives this message, then the RPL owner starts the WTR timer. When the WTR timer expires, the RPL owner sends out a R-APS (NR, RB), blocks the RPL, and flushes the FDB. Other nodes in the topology that receive the R-APS (NR, RB) unblock any non-failed port and flush the FDB.

In order to clear the MS condition, the operator must enter the manual switch command from ERN3. Refer to the following table for the event sequence.

Table 1. MS on Non-RPL node event sequence

Non-RPL node with error (ERN3)

RPL owner (ERN 1) and RPL node (ERN2)

Other Non-RPL node (ERN4)

From the Idle state, ERN3:

  1. Blocks the MS port.
  2. Sends the RAPS (MS).
  3. Flushes the FDB.
  4. Enters the manual switch (MS) state.

From the Idle state, ERN4:

  1. Forward R-APS (MS).
  2. Flush the FDB.
  3. Enter the MS state.

From the Idle state, ERN 1:

  1. Forwards R-APS (MS).
  2. Unblocks the RPL.
  3. Flushes the FDB.
  4. Enters the MS state.

After the manual switch is triggered, the operator can clear it with the no command and MS recovery will begin. Refer to the following table for the event sequence.

Table 2. MS recovery process event sequence

Non-RPL node with error (ERN3)

RPL owner (ERN1)

RPL node (ERN2) with dual-end blocking enabled

Non-RPL node (ERN4)

From the MS state, ERN3:

  1. Stops sending R-APS (MS).
  2. Sends R-APS (NR).
  3. Continues to block the port.
  4. Enters the Pending state.

From the MS state, ERN1:

  1. Receives the R-APS (NR).
  2. Starts the WTB timer.
  3. Forwards the R-APS (NR).
  4. Enters the Pending state.
  5. After the WTB timer expires, blocks the RPL.
  6. Flushes the FDB.
  7. Sends R-APS (NR, RB).
  8. Enters the Idle state.

From the MS state, ERN2:

  1. Receives the R-APS (NR).
  2. Forwards the R-APS (NR).
  3. Enters the Pending state.

From the MS state, ERN2:

  1. Receives the R-APS (NR).
  2. Forwards the R-APS (NR).
  3. Enters the Pending state.

From the Pending state, ERN3:

5. Receives the R-APS (NR, RB) and unblocks the blocking port.

6. Forwards the R-APS (NR, RB).

7. Flushes the FDB.

8. Enters the Idle state.

From the Pending state, ERN2:

4. Blocks the RPL.

5. Forwards the R-APS (NR, RB).

6. Flushes the FDB.

7. Enters the Idle state.

From the Pending state, ERN4:

4. Forwards the R-APS (NR, RB).

5. Flushes the FDB.

6. Enters the Idle state.
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