To ensure that a stack can be set up successfully, you are advised to familiarize yourself with stack setup precautions before setting up a stack.

• Optical or copper modules that are certified for Huawei Ethernet switches must be used. If high-speed cables or AOCs are used, you must purchase cables from Huawei.

  Optical or copper modules that are not certified for Huawei Ethernet switches or cables that are not purchased from Huawei cannot ensure transmission reliability and may affect service stability. Huawei is not liable for any problem caused by the use of optical or copper modules that are not certified for Huawei Ethernet switches, or cables not purchased from Huawei, and will not fix such problems.

• To ensure high network reliability, it is recommended that a stack connect to upstream and downstream devices using an inter-device Eth-Trunk (dual-homing networking).
• Before setting up a stack, you are advised to load the same software version and patch version on member switches.
• It is recommended that you use two or more links to set up a stack. If only one link is used to set up a stack (this method is not recommended), it is recommended that you run the carrier down-hold-time interval command on stack member ports to configure the delay after which the port Down state is reported to prevent the stack from becoming unstable because of intermittent port disconnection.
• Before the master and standby switches complete batch backup, do not shut down or remove stack links to prevent switch restart.

  To check the batch backup status between master and standby switches, run the display switchover state command.

• To prevent stack packet forwarding from being affected, you are advised not to configure the flow-control command on stack member ports.
• When traffic control is configured in a stack and traffic is forwarded between member switches in the stack, traffic control does not take effect because stack ports do not support the flow-control command.
• In V100R006C00 or later versions, after service ports are configured as stack member ports, the port crc-statistics trigger error-down command is automatically configured on these member ports. After a version upgrade to V100R006C00 or later, the port crc-statistics trigger error-down command configuration is automatically added to these member ports.

  In versions earlier than V200R002C50, after stack member ports are restored as common service ports, the port crc-statistics trigger error-down command configuration is not automatically

  cleared.

  In V200R002C50 and later versions, if the port crc-statistics trigger error-down command is not configured before service ports are configured as stack member ports, this command configuration is automatically cleared after stack member ports are restored as common service ports. If this command has been configured before service ports are configured as stack member ports, this command configuration is not automatically cleared after stack member ports are restored as service ports.

• When the protocol of a stack member port is Down, the port will not enter the error-down state due to CRC error packets.
• On the CE6880EI, only known unicast and multicast packet statistics on stack member ports are collected, and unknown unicast packet statistics are collected as multicast packet statistics.
• In a stack, support for most features except the following features is the same as support on a single device. Table 3-3 shows the difference in support for some features.