Sdm Prefer - Cisco Catalyst 3750 Command Reference Manual

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
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.
•
•
•
Note For more information about stacking, see the "Managing Switch Stacks" chapter in the software
configuration guide.
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.
Do not use the routing template if you do not have routing enabled on your switch. Entering the sdm
prefer routing [desktop] global configuration command prevents other features from using the memory
allocated to unicast routing in the routing template.
Table 2-15
desktop or aggregator switch. The first eight rows in the tables (unicast MAC addresses through security
ACEs) represent 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. The last row is a guideline used to calculate hardware resource consumption related to the
number of Layer 3 VLANs configured.
Table 2-15 Approximate Number of Feature Resources Allowed by Each Template
Resource
Unicast MAC addresses
Internet Group Management Protocol
(IGMP) groups and multicast routes
Unicast routes
Directly connected hosts
•
• Indirect routes
Policy-based routing access control
entries (ACEs)
QoS classification ACEs
78-16181-03
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 stack master, the stack operates with the desktop template selected on the stack
master. This could cause configuration losses on the Catalyst 3750-12S stack member if the number
of TCAM entries on it exceeds desktop template sizes.
lists the approximate number of each resource supported in each of the three templates for a
Desktop Templates
Default
6 K
1 K
8 K
6 K
2 K
0
512
Routing VLAN
3 K 12 K
1 K 1 K
11 K 0
3 K 0
8 K 0
512 0
512 512
Catalyst 3750 Switch Command Reference
Aggregator Templates
Default Routing
6 K 6 K
1 K 1 K
12 K 20 K
6 K 6 K
6 K 14 K
0 512
896 512

sdm prefer

VLAN
12 K
1 K
0
0
0
0
896
2-283