Cisco Catalyst 3560X-24P Command Reference Manual page 523

Chapter 2 Catalyst 3750-X and 3560-X Cisco IOS Commands
Usage Guidelines You must reload the switch for the configuration to take effect. If you enter the show sdm prefer
command before you enter the reload privileged EXEC command, the show sdm prefer command
shows the template currently in use and the template that will become active after a reload.
Follow these guidelines for switch stacks:
•
•
•
Use the no sdm prefer command to set the switch to the default template.
The access template maximizes system resources for access control lists (ACLs) as required to
accommodate a large number of ACLs.
The default templates balances the use of system resources.
Use the sdm prefer vlan global configuration command only on switches intended for Layer 2 switching
with no routing. When you use the VLAN template, no system resources are reserved for routing entries,
and any routing is done through software. This overloads the CPU and severely degrades routing
performance.
Do not select a routing template (sdm prefer routing or sdm prefer dual-ipv4-and-ipv6 routing) when
the switch is running the LAN base feature set. Although visible in the command-line help, the LAN
base feature set does not support routing. On switches running the LAN base feature set, routing values
shown in all templates are not valid.
Do not use the routing template if you do not have routing enabled on your switch. Entering the sdm
prefer routing global configuration command prevents other features from using the memory allocated
to unicast routing in the routing template.
Do not use the ipv4-and-ipv6 templates if you do not plan to enable IPv6 routing on the switch. Entering
the sdm prefer ipv4-and-ipv6 {default | routing | vlan} global configuration command divides
resources between IPv4 and IPv6, limiting those allocated to IPv4 forwarding.
Table 2-23
templates for a switch. The values in the template are based on 8 routed interfaces and 1024 VLANs and
represent the approximate hardware boundaries set when a template is selected. If a section of a
hardware resource is full, all processing overflow is sent to the CPU, seriously impacting switch
performance.
On switches running the LAN base feature set, routing values shown in all templates are not valid.
Note
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In a switch stack, all stack members use the same SDM desktop template that is stored on the stack
master. When a new switch member is added to a stack, the stored SDM configuration overrides the
template configured on an individual switch.
The IPv6 packets are routed in hardware across the stack, as long as the packet does not have
exceptions (IPv6Options) and the switches have not run out of hardware resources.
If a stack member cannot support the template that is running on the master switch, the switch goes
into SDM mismatch mode, the master switch does not attempt to change the SDM template, and the
switch cannot be a functioning member of the stack.
For more information about stacking, see the "Managing Switch Stacks" chapter in the software
configuration guide.
lists the approximate number of each resource that is supported in each of the IPv4-only
Catalyst 3750-X and 3560-X Switch Command Reference
sdm prefer
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