Appendix B

About Switch Stacking

•If the incoming unit did not have an assigned Unit ID (that is, it was in factory default mode), it will be assigned the lowest available Unit ID by the Master. It is strongly recommended that automatic assigned unit ID mode be used since it provides better resiliency to the stack.

•If the incoming unit already has an assigned Unit ID, and that Unit ID is unused in the current stack, the incoming unit will keep its assigned Unit ID and the Master will apply to it any configuration relevant to that Unit ID.

•If the incoming unit already has an assigned Unit ID, and that Unit ID conflicts with a unit ID in the current stack, the Master will reallocate a new Unit ID to the incoming unit, giving it the lowest available Unit ID (assuming, of course, that the incoming unit does not have a manually assigned Unit ID, which the Master cannot change).

•If the incoming unit cannot be assigned an available Unit ID for any reason (in the case of unit replacement that can only happen if the incoming unit has a manually assigned Unit ID), then it will be effectively shut down—that is, it will not be joined to the stack.

3.The stack Master will now carry out Unit and port configuration for the incoming unit.

•Any configuration information the Master has that is relevant to the number assigned to the incoming unit will be applied. In particular, if the incoming unit was assigned the same Unit ID of the unit it replaces, then it will receive the same configuration as the failed unit, to the extent possible.

If the incoming unit is identical in makeup to the replaced unit, the entire configuration of the replaced unit will be applied to the incoming one and the stack will go back to the state it was in before unit failure. However, sometimes the incoming unit is not identical to the unit that failed in these cases. The stack Master will apply the configuration in the following manner:

•If a 24-port unit replaces a failed 48-port unit, then the ports of the incoming unit will be configured according to the way the first 24 ports of the failed unit were configured.

(Note that the configuration of all 48 ports of the failed unit is remembered, even though only the first 24 are currently applied. If, in the future, a 48 port unit is inserted and assigned the same Unit ID, it will be configured as the original failed 48- port unit was configured).

•If a 48-port unit replaces a 24-port unit, then the first 24 ports of the incoming unit will be configured according to the way the ports of the failed unit were configured, and the rest of the ports of the incoming unit will be configured at default settings.

•If the units (the failed one and its replacement) had/have uplink ports, then the first uplink of the incoming unit will be configured as was the first uplink of the failed unit, and so on.

Stack Master Failure and Replacement

In this example, the master unit fails in a running stack. When notified of the failure, a system administrator removes the failed unit and replaces it with another one.

When the unit fails, the stack Backup Master detects (via the ongoing monitoring Master Discovery process) that the master unit no longer responds and takes over as the stack master. The backup master directs all other stack members to route unit-to-unit traffic around the failed unit using the ring topology of the stacking connections. At the same time the stack Backup Master notifies the system administrator (using SYSLOG messages and SNMP traps) of the failure.

When the failed unit is disconnected from the stack, all traffic will already be routed around it, and as long as all other stacking connections are left intact, the stack should continue to run.

When a new unit is inserted in the stack and powered up, the following will happen:

1.The incoming unit will perform Master discovery, and perhaps participate in a Master Election, as described above.

•If the incoming unit has a Unit ID of 1 or 2 (that is, the unit is a master-enabled unit), then Master Election will be initiated. However, since the running stack Backup Master has a longer run time, assuming that it has been running for more then 10 minutes, it will remain elected as the stack Master and the incoming unit will not become a new stack Master. This may result in an incoming unit using Unit ID=1, and serving as the stack backup master, while the already running unit with Unit ID=2 remains the active stack master.

2.The stack Master at this stage will carry out a Unit ID allocation and conflict resolution process.

•If the incoming unit did not have an assigned Unit ID (that is, it was in factory default mode), it will be assigned the lowest available Unit ID by the Master. It is strongly recommended that automatic assigned unit ID mode be used since it provides better resiliency to the stack.

24/48-Port 10/100 + 4-Port Gigabit Resilient Clustering Smart Switch with 2 Combo SFPs

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Linksys SLM224G4S manual Stack Master Failure and Replacement
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SLM224G4S specifications

The Linksys SLM224G4S is a sophisticated Layer 2 managed switch designed for businesses and institutions that demand high performance, reliability, and advanced networking features. This model stands out due to its blend of robustness and manageability, making it ideal for expanding networks.

One of the primary features of the SLM224G4S is its 24 Gigabit Ethernet ports, allowing for high-speed data transfers essential for bandwidth-intensive applications. Supporting auto-negotiation, these ports can detect the capabilities of connected devices and configure themselves accordingly, ensuring optimal performance without manual intervention. With four additional shared Gigabit SFP (Small Form-factor Pluggable) ports, this switch provides flexibility in network design and enhances scalability.

The SLM224G4S supports VLAN (Virtual Local Area Network) capabilities, which can segment network traffic to improve security and performance. This is particularly useful in environments where different departments or teams require distinct network segments for operational efficiency. By implementing VLANs, organizations can enhance their network management while isolating sensitive information from potential threats.

Quality of Service (QoS) is another critical technology integrated into the SLM224G4S. It prioritizes network traffic, ensuring that critical applications receive the bandwidth they need for optimal performance. This is particularly important for VoIP and video conferencing applications, where latency and jitter can significantly impact user experience.

The switch also features advanced Layer 2 management functionalities, including SNMP (Simple Network Management Protocol), allowing IT administrators to monitor network performance and quickly troubleshoot issues. The embedded web-based management interface makes configuration straightforward, enabling quick adjustments to settings without deep networking knowledge.

Security is a paramount consideration in today’s networking landscape. The SLM224G4S provides robust security features, including port security that limits the number of MAC addresses allowed on a port, reducing the risk of unauthorized access. Moreover, it supports802.1X port-based authentication, ensuring that only authenticated devices can connect to the network.

In summary, the Linksys SLM224G4S managed switch boasts features such as 24 Gigabit Ethernet ports, VLAN support, QoS, SNMP management, and advanced security protocols. These characteristics make it an excellent choice for businesses looking to enhance their network's performance, safety, and reliability, paving the way for seamless connectivity in today’s digital age.
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