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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
sdm prefer
Command History
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.
Desktop switches support only desktop templates; an aggregator switch (Catalyst 3750-12S) supports
both desktop and aggregator templates. On an aggregator switch, if you do not enter the desktop
keyword, the aggregator templates are selected.
All stack members use the same SDM desktop or aggregator template, stored on the stack master. When
a new switch member is added to a stack, as with the switch configuration file and VLAN database file,
the SDM configuration that is stored on the master overrides the template configured on an individual
switch.
To route IPv6 packets in a stack of switches, all switches in the stack should be running the IP services
image. 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 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.
• If the master switch is a Catalyst 3750-12S, and you change the template from an aggregator
template to a desktop template and reload the switch, the entire stack operates with the selected
desktop template. This could cause configuration losses if the number of ternary content addressable
memory (TCAM) entries exceeds the desktop template sizes.
• If you change the template on a Catalyst 3750-12S master from a desktop template to an aggregator
template and reload the switch, any desktop switches that were part of the stack go into SDM
mismatch mode.
• If you add a Catalyst 3750-12S switch that is running the aggregator template to a stack that has a
desktop switch as the master, the stack operates with the desktop template selected on the master.
This could cause configuration losses on the Catalyst 3750-12S member if the number of TCAM
entries on it exceeds desktop template sizes.
For more information about stacking, see the “Managing Switch Stacks” chapter in the software
configuration guide.
The access template maximizes system resources for access control lists (ACLs) as required to
accommodate a large number of ACLs.
The default templates balance the use of system resources.
Use the sdm prefer vlan [desktop] 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.
Release Modification
12.1(11)AX This command was introduced.
12.1(14)EA1 The aggregator templates were added.
12.2(25)SEA The dual-ipv4-and-ipv6 templates were added.
12.2(25)SED The access templates were added.
12.2(25)SEE The dual-ipv4-and-ipv6 routing template was added.
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