WeOS
5.29.0

# HSR and PRP HowTo guide

This document, being a non-exhaustive guide, outlines some practical examples of how to configure and use High-Availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP).

For an overview of what HSR/PRP is and how it may be used, refer to:

- High-Availability Seamless Redundancy (HSR) and Parallel Redundancy Protocol (PRP)

Westermo RedBox supports the types `hsr` (HSR-SAN), `prp` (PRP-SAN), and `hsr-prp` (HSR-PRP). Set the RedBox type with the command `type`. The ports are automatically selected, as the RedBox has dedicated ports for A, B, and interlink. The ports are labelled as such on the front plate.

    redbox:/config/hsr-prp-1/#> show
    Enabled                : YES
    Type                   : HSR
    Mode                   : H
    Supervision frames     : YES
    Life check interval    : 2 s
    Entry forget time      : 6 (640 ms)
    Node reboot interval   : 500 ms
    Proxy node forget time : 64 s
    Node forget time       : 64 s
    Port A                 : ethA
    Port B                 : ethB
    Multicast octet        : 00

## Basic HSR setup

A basic HSR setup only requires creating an instance of the type.

    redbox:/#> config hsr-prp 1
    redbox:/config/hsr-prp-1/#> type hsr
    redbox:/config/hsr-prp-1/#> leave
    redbox:/#>

Figure 1 shows a basic HSR ring setup. The ring can be expanded with more HSR devices, and provides seamless failover on link failure.

                +---------+
                |         |
                |   SAN   |
                |         |
                +----+----+
                     |
                     |
                +----I----+
                |         |
                | redbox  |
          +-----A HSR-SAN B------+
          |     |         |      |
          |     +---------+      |
          |                      |
          |                      |
          |     +---------+      |
          |     |         |      |
          +-----A redbox  B------+
                | HSR-SAN |
                |         |
                +----I----+
                     |
                     |
                +----+----+
                |         |
                |   SAN   |
                |         |
                +---------+

Figure 1: Two SAN devices connected redundantly via two HSR-SAN RedBoxes.

## HSR-PRP coupling setup

Figure 2 shows a setup with three of the possible RedBox modes. LAN A and LAN B may contain other PRP and non-PRP devices that have redundancy through the ring.

                +---------+
                |         |
                |   SAN   |
                |         |
                +----+----+
                     |
                     |
                +----I----+
                |redbox-1 |
                |         |
          +-----A PRP-SAN B------+
          |     |         |      |
          |     +---------+      |
          |                      |
    +~~~~~~~~~~~~+       +~~~~~~~~~~~~+
    |            |       |            |
    |            |       |            |
    |   LAN A    |       |    LAN B   |
    |            |       |            |
    |            |       |            |
    +~~~~~~~~~~~~+       +~~~~~~~~~~~~+
          |                      |
          |                      |
          |                      |
    +-----I---+             +----I----+
    |redbox-2 |             |redbox-3 |
    |         |             |         |
    | HSR-PRP A-------------A HSR-PRP |
    |         |             |         |
    +-----B---+             +----B----+
          |                      |
          |     +---------+      |
          |     |redbox-4 |      |
          +-----A         B------+
                | HSR-SAN |
                |         |
                +----I----+
                     |
                     |
                +----+----+
                |         |
                |   SAN   |
                |         |
                +---------+

Figure 2: A PRP-SAN RedBox connects a SAN redundantly to an HSR ring, with another SAN device attached at the other side of the ring.

Note: The configuration in Figure 2 is not valid if redbox-2 and redbox-3 are PTP Transparent Clocks, as IEC 62439-3:2016 does not specify how a TC should behave in such a situation.

Configure the LAN ID of the HSR-PRP interlink ports with the respective LAN they connect to, and the Net ID (PRP ID) to the same for both because those A and B are associated with each other. The Net ID prevents frames from LAN A from being sent to LAN B, and vice versa.

A completely separate PRP network also connected to the ring must have another Net ID, as those frames may still enter other PRP networks. The standard specifies a total of 6 possible PRP networks in a single topology (values 1-6, HSR-SAN devices like redbox-4 use the value 0, 7 is reserved for future use).

Below is the configuration for each of the devices in Figure 2.

    redbox-1:/#> config hsr-prp 1
    redbox-1:/config/hsr-prp-1/#> type prp
    redbox-1:/config/hsr-prp-1/#> leave
    redbox-1:/#>

    redbox-2:/#> config hsr-prp 1
    redbox-2:/config/hsr-prp-1/#> type hsr-prp
    redbox-2:/config/hsr-prp-1/#> lan-id A
    redbox-2:/config/hsr-prp-1/#> prp-id 1
    redbox-2:/config/hsr-prp-1/#> leave
    redbox-2:/#>

    redbox-3:/#> config hsr-prp 1
    redbox-3:/config/hsr-prp-1/#> type hsr-prp
    redbox-3:/config/hsr-prp-1/#> lan-id B
    redbox-3:/config/hsr-prp-1/#> prp-id 1
    redbox-3:/config/hsr-prp-1/#> leave
    redbox-3:/#>

    redbox-4:/#> config hsr-prp 1
    redbox-4:/config/hsr-prp-1/#> type hsr
    redbox-4:/config/hsr-prp-1/#> leave
    redbox-4:/#>

## Multiple rings

Each PRP LAN can connect to multiple rings for more redundancy.

    +~~~~~~~+      +~~~~~~~+
    | LAN A |      | LAN B |
    | Net 1 |      | Net 1 |
    +~~~~~~~+      +~~~~~~~+
        |    \    /    |
        |     \  /     |
        |      \/      |
        |      /\      |
        |     /  \     |
        |    /    \    |
    +~~~~~~~+      +~~~~~~~+
    |       |      |       |
    |Ring 1 |      |Ring 2 |
    |       |      |       |
    +~~~~~~~+      +~~~~~~~+

Figure 3: PRP LANs connected to two separate rings.

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