Cisco Catalyst 3750-X Command Reference Manual page 576

sdm prefer
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.
Although these templates are visible on all switches, the resources on switches running the LAN base
feature do not match those shown in the templates:
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Follow these guidelines for switch stacks:
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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, sdm prefer dual-ipv4-and-ipv6 routing, or
indirect-ipv4-and-ipv6-routing) when the switch is running the LAN base feature set. The LAN base
feature set supports 16 static IPv4 routes on SVIs when the switch is running the default template.
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.
Use the indirect-ipv4-and-ipv6-routing template to provide more space for IPv4 and IPv6 summary or
indirect routes by providing less space for IPv4 policy-based routing entries and IPv6 ACL, QoS, and
policy-based routes.
You can verify your settings by entering the show sdm prefer privileged EXEC command.
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Switches running the LAN base feature set support only 255 VLAN s, not 1024 as shown in all
templates.
Although the routing template is visible, the template is not supported.
The LAN base feature set supports only 16 static IPv4 routes on SVIs and the switch must be
running the default template for static routing.
On switches running the LAN base feature set, none of the routing values shown for the templates
are valid.
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.
Chapter 2 Catalyst 3750-X and 3560-X Switch Cisco IOS Commands
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