Cisco Stack Modules C2960S-STACK Switchs Cable CAB-STK-E-3M= 3M C2960S-STACK Features: Figure 1. Comparison of FlexStack and Nonstacked Configurations Stacking Ethernet switches provides the network administrator with three major operational benefits: в—Џ Single point of management: All switches in the stack are managed as one. в—Џ Built-in redundancy and high availability: The high-speed FlexStack connections provide redundant communication for each stack member to every other member. в—Џ Scalability to fit network needs: Installation of a new switch to the stack is easy. As the need for additional access ports grows, adding a new switch to an existing stack is easier and faster than adding a new standalone switch to the network. The first operational benefit is fewer devices to manage. Multiple physical switches in a stack appear as a single logical switch. This eases management overhead because there are fewer devices in the network to manage. A single IP address is used to manage the logical switch. All manageable entities (for example, Ethernet interfaces and VLANs) on all physical switches can be configured and managed from the logical switch. The logical switch will appear as a single entity in the network. In a Layer 2 network, the logical switch will appear as a single spanning-tree entity. The second operational benefit that stacking provides is built-in redundancy and increased availability. Data path redundancy is built into the stacking architecture as there are two physical paths between any two stack members. Connecting stack members with the stacking cables provides data path redundancy for all stack members. Stacking increases Ethernet switch availability by providing redundancy for both the physical switch and the uplink. Because different physical switches will connect to the upstream network, losing one switch or one uplink interface does not prevent connectivity to the network. Since the logical switch has multiple uplinks, the logical switch still has network connectivity because at least one uplink is still active. In a logical switch, a single physical switch is acting as the stack master. The stack master manages all physical switches, including itself. If the master fails, another member automatically becomes the stack master following a well-documented election process (covered later). The configuration of the stack is preserved through a single switch failure or a reboot of all stack members. FlexStack provides 1:N redundancy for the stack master, with the ability for any physical switch to back up the acting master. (See Figure 2.) Figure 2. FlexStack with Redundant Links Flexibility of FlexStack allows for modular stacking capability. Cisco Catalyst 2960 switches can be added to a stack at any time by adding the optional FlexStack module. As the demand for Ethernet access ports increases, Cisco Catalyst 2960 switches can be stacked together either to create a new stack or to add new Cisco Catalyst 2960 switches to an existing stack. This flexibility provides investment protection for the network administrator, who can add additional stack members as needed. Adding members to a stack and replacing physical units are much easier when multiple switches are combined into a FlexStack group. Since the stack retains the configuration, there is no need to back up the configuration prior to removing the switch. Conversely, when a new member is inserted into the stack, the configuration of the stack is pushed to the new member. The network administrator need not explicitly recover the switch configuration since the stack took care of it. Stacking and Clustering Stacking is not clustering. Clustering is a technology available on Cisco Catalyst fixed Ethernet switches that allows the network administrator to use a single public IP address to manage multiple physical switches. Clustering was created to assist network administrators by having a single point of management as well as in preserving valuable public IP addresses needed to manage the Ethernet switches. Stacking is much more than a single point of management and IP address preservation because it offers redundancy, availability, and ease of management. Cisco Catalyst 2960 supports clustering as well as stacking. Pictures for reference:
