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Stack Features
Cisco Catalyst 2960-S
FlexStack Stacking
Cisco Catalyst 2960-X
FlexStack-Plus Stacking
Cisco Catalyst 3750-X
StackWise Plus
Cisco Catalyst 3850
StackWise- 480
Dynamic ring load
balancing
No
No
Yes
Yes
Stack convergence
1-2 seconds
100 milliseconds
Few milliseconds
Few milliseconds
Stack link failure detection
Software
Hardware
Hardware
Hardware
Stack quality of service
(QoS)
Applied hop by hop
Applied hop by hop
Applied on ingress
Applied on ingress
Management
Single IP address, SNMP,
syslog
Single IP address, SNMP,
syslog
Single IP address, SNMP,
syslog
Single IP address, SNMP,
syslog
Configuration
Single config and CLI, auto
image and config update
Single config and CLI, auto
image and config update
Single config and CLI, auto
image and config update
Single config and CLI, auto
image and config update
Show and debug
commands
Unified
Unified
Unified
Unified
Single forwarding and
control plane
Synchronize Address
Resolution Protocol (ARP),
MAC address, Internet
Group Management
Protocol (IGMP), VLAN
tables
Synchronize ARP, MAC
address, IGMP, VLAN
tables
Synchronize ARP, MAC
address, IGMP, VLAN
tables, routing tables
Synchronize ARP, MAC
address, IGMP, VLAN
tables, routing tables
Cross-stack features
Yes
Yes
Yes
Yes
Single bridge ID
Yes
Yes
Yes
Yes
Redundancy
Stack master 1:N
redundancy
Stack master 1:N
redundancy
Stack master 1:N
redundancy
Stack active master with
single standby
predetermined
The differences between FlexStack, FlexStack-Plus, and StackWise-480 are rooted in the different hardware
architectures. StackWise-480 is the superior architecture. StackWise-480 is a dual redundant ring architecture with
individual links operating at 240Gbps bidirectionally. The StackWise-480 connections are not pure Ethernet links
but rather a dual ring architecture, allowing packets to take either ring. The FlexStack and FlexStack-Plus links are
full duplex 10Gbps or 20Gbps Ethernet links. The ring architecture gives StackWise-480 a significant advantage
over FlexStack and FlexStack-Plus when it comes to high availability of the stack.
In Table 5 stack convergence is measured in milliseconds for StackWise-480, as opposed to seconds for
FlexStack. This is because of the ring architecture. In StackWise-480 packets ingressing the stack can be
forwarded on either ring. When one ring becomes inoperable, all ingressing packets are forced to a single ring. The
speed of one ring is 240Gbps and can easily accommodate an entire stack. The recovery time for a single link
going inoperable is not dependent upon the number of members in the stack. It is consistent across all stack sizes.
In FlexStack, when a single link becomes inoperable, there is a stackwide disruption in the forwarding of packets.
The members must rediscover the new topology. This rediscovery time can take up to 1 to 2 seconds depending
upon the number of members in the stack. Smaller stacks will reconverge more quickly than larger stacks.
Because FlexStack and FlexStack-Plus stack links are Ethernet links, forwarding packets from one stack member
to another requires the packets to be forwarded by each member. This is referred to as hop by hop, meaning the
packets must hop from the ingressing member to the egressing member across all members in between.
Not all members see the packet. Only those members in the data path will forward the packet. This hop-by-hop
behavior is the same as different Ethernet switches forwarding the packet among themselves. Hop by hop requires
that each member must queue the packet. Queuing the packet means that QoS is applied at each hop. If a stack
link between two members becomes congested, packets that successfully ingress on one member may be
discarded by another member because of that congestion. There is no dynamic adjustment to the forwarding of
packets when one link becomes congested.