Huawei CE Series Switches Stack Configuration Notes

Huawei CE series switches (CE6855-48S6Q-HI, CE8850-32CQ-EI, CE12804S etc.) can set up a stack to improve forwarding performance and reliability. In this article, we will introduce the definition of a stack and purpose of setting up a stack.

Definition

A cluster switch system (CSS) is also called a stack. (The term stack is used throughout this document.) Stacking technology combines two switches into a virtual switching device, as shown in Figure 1.

Figure 1 Schematic diagram of a stack

Purpose

Stacking technology provides high network reliability and scalability, while simplifying network management.

• High reliability: Member switches in a stack work in redundancy mode. Inter-device Eth-Trunk links can also be set up between the member switches to implement link redundancy.
• High scalability: By combining physical switches into a stack, you can easily increase the number of ports, bandwidth, and processing capability without changing the network topology.
• Simple configuration and management: You can log in to a stack from any member switch to manage and configure all the member switches in the stack. In addition, complicated Layer 2 ring protection protocols (such as MSTP) or Layer 3 protection switching protocols (such as VRRP) are not required after switches set up a stack; therefore, the network configuration is much simpler.

Concepts

Figure 2 shows the roles and related concepts in a stack.

Figure 2 Roles and concepts in a stack

• Roles

Switches that have joined a stack are member switches. Each member switch in a stack plays one of the following roles:

1.  Master switch

The master switch manages the entire stack. A stack has only one master switch.

2.  Standby switch

The standby switch is a backup of the master switch. When the master switch fails, the standby switch takes over all services from the master switch. A stack has only one standby switch.

• Stack domain

  After switches are connected using stack links and set up a stack, they form a stack domain. Multiple stacks can be deployed on a network to support various applications. These stacks are identified by their domain IDs.

  

   

• Stack member ID

  Stack member IDs are used to identify and manage member switches in a stack. Each member switch in a stack has a unique member ID.

   

• Stack priority

  The stack priority of a member switch determines the role of the member switch in role election. A larger value indicates a higher priority and higher probability that the member switch is elected as the master switch.

   

• Physical member port

  After the mode of a physical port is set to stack, the port becomes a physical member port. Physical member ports are used to connect stack member switches.

• Stack port

  A stack port is a logical port exclusively used for stacking and includes several physical stack ports. Multiple physical member ports can be added to a stack port to improve stack link bandwidth and reliability.

  Each switch supports one stack port. Before the stacking function is enabled, the stack port is named Stack-Port1. After the stacking function is enabled, the stack port is named Stack-Port n/1, where n is the stack member ID of the switch.

Stack Connection Modes

Links in a stack fall into two types: management links and forwarding links. Management links are used to forward management packets of the stack, and forwarding links are used to forward service packets between stack member switches. Stack member switches can be connected in two modes: main processing unit (MPU) connection and line processing unit (LPU) connection, distinguished by the connections of management links. Figure 3 shows the two stack connection modes.

Figure 3 Stack connection modes

• In MPU connection mode, management links and forwarding links are separated. Management links are connected through the system inter-connect ports (SIPs) on MPUs, and forwarding links are connected through ports on LPUs.
• In LPU connection mode, management links and forwarding links are integrated and both connected through ports on LPUs. SIP ports on the MPUs are not connected.

Table 1 Comparisons between the two connection modes

NOTE:

V100R001C00 supports only the MPU connection mode.

You are advised to preferentially use the MPU connection mode. This mode separates management links from forwarding links, ensuring high reliability of the stack system.

SIP Port Connections

SIP ports are located on MPUs. Each MPU has two SIP ports, as shown in Figure 4. A SIP port is a combo port consisting of a GE electrical port and a GE optical port. It starts to work immediately after a cable is connected and does not require any configuration. By default, the working mode of a combo port depends on whether the electrical port or optical port has a cable connected first. If the electrical and optical ports are connected at the same time, the combo port works as an optical port.

NOTE: 

After a copper module that does not have a cable connected is installed in the optical port of a SIP port on a CE12800S MPU, the optical port becomes Down and will not change into an electrical port. You need to remove the copper module so that the electrical port can become Up.

Figure 4 SIP ports on an MPU

Figure 5 shows the recommended SIP port connections when each stack member switch has two MPUs.

Figure 5 SIP port connections

NOTE:

Each switch must have at least one SIP port connected.

A SIP port on one switch can only be connected to a SIP port on the other switch, and cannot be connected to other SIP ports on the same switch.

Service Port Connections

A logical stack port can contain physical member ports on the same LPU or different LPUs. A maximum of 32 physical member ports can be added to a stack port to improve stack link bandwidth and reliability. Two networking modes are available according to the distribution of member ports, as shown in Figure 6.

Figure 6 Service port connections

1+1 networking: Physical member ports are located on one LPU. Connect the two LPUs of the two switches to form a stack.

N+M networking (N ? 2, M ? 2): Physical member ports are located on multiple LPUs, and stack links of different LPUs back up each other.

NOTE: 

The N+M networking is more reliable and is recommended.

In N+M networking, physical member ports on an LPU of the local switch can only be connected to physical member ports on the same LPU but not different LPUs of the peer switch. Physical member ports cannot be connected in other manners to avoid the connection as shown in Figure 7.

Figure 7 Incorrect service port connection mode

NOTE: 

Local physical member ports cannot connect to remote common service ports. Otherwise, traffic forwarding may fail or the device restarts unexpectedly. Ports on both ends must be configured as physical member ports or service ports simultaneously.

From the above article, I believe you have mastered the definition of a stack and purpose of setting up a stack. Hope it can help you when you need to set up a stack to improve forwarding performance and reliability. If any question, please feel free to contact: supports@thunder-link.com