Switch Stacking and Chassis Aggregation

Switch Stacking and Chassis Aggregation

1. Switch Stacking

   • It is often used and offered by Cisco in switches meant for the access layer. If a switch stack is made: -The stack would have a single management IP address. -The engineer would connect with Telnet or SSH to one switch (with that one management IP address), not multiple switches. -One configuration file would include all interfaces in all four physical switches. -STP, CDP, VTP would run on one switch, not multiple switches. -The switch ports would appear as if all are on the same switch. -There would be one MAC address table, and it would reference all ports on all physical switches.
   • The stacking cables together make a ring between switches. That is, the switches connect in series, with the last switch connecting again to the first. Using full duplex on each link. The stack cables are short, with the expectation that the switches sit together in the same room and rack.
   • Cisco FlexStack
     • Year introduced: 2010 Switch model series: 2960-S, 2960-X Speed of single stack link, in both directions (full duplex): 10 Gbps Maximum number of switches in one stack: 4
   • Cisco FlexStack-Plus
     • Year introduced: 2013 Switch model series: 2960-X, 2960-XR Speed of single stack link, in both directions (full duplex): 20 Gbps Maximum number of switches in one stack: 8
   • Stack Master
     • One switch acts as a stack master to control the rest of the switches.

2. Chassis Aggregation

   • -Typically is used for higher-end switches used as distribution or core switches. -Does not require special hardware adapters, instead using Ethernet interfaces. -Aggregates two switches. -Arguably is more complex but also more functional.
   • Cisco's Virtual Switching System (VSS) that is supported on 6500 and 6800 series switches.
   • The following list describes some of the advantages of using switch aggregation. Note that many of the benefits should sound familiar from the switch stacking discussion. The one difference in this list has to do with the active/active data plane. Multichassis EtherChannel (MEC): Uses the EtherChannel between the two physical switches. Active/Standby Control Plane: Simpler operation for control plane because the pair acts as one switch for control plane protocols: STP, VTP, EtherChannel, ARP, routing protocols. Active/Active data plane: Takes advantage of forwarding power of supervisors on both switches, with active Layer 2 and Layer 3 forwarding the supervisors of both switches. the switches synchronize their MAC and routing tables to support that process. Single switch management: Simpler operation of management protocols by running management protocols (Telnet, SSH, SNMP) on the active switch; configuration is synchronized automatically with the standby switch.