Cisco Catalyst 3750-X User Manual

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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 22 Configuring Optional Spanning-Tree Features
Understanding Optional Spanning-Tree Features
At the interface level, you enable BPDU guard on any port by using the spanning-tree bpduguard
enable interface configuration command without also enabling the Port Fast feature. When the port
receives a BPDU, it is put in the error-disabled state.
The BPDU guard feature provides a secure response to invalid configurations because you must
manua
lly put the interface back in service. Use the BPDU guard feature in a service-provider network
to prevent an access port from participating in the spanning tree.
Understanding BPDU Filtering
The BPDU filtering feature can be globally enabled on the switch or can be enabled per interface, but
the feature operates with some differences.
At the global level, you can enable BPDU filtering on Port F
ast-enabled interfaces by using the
spanning-tree portfast bpdufilter default global configuration command. This command prevents
interfaces that are in a Port Fast-operational state from sending or receiving BPDUs. The interfaces still
send a few BPDUs at link-up before the switch begins to filter outbound BPDUs. You should globally
enable BPDU filtering on a switch so that hosts connected to these interfaces do not receive BPDUs. If
a BPDU is received on a Port Fast-enabled interface, the interface loses its Port Fast-operational status,
and BPDU filtering is disabled.
At the interface level, you can enable BPDU filtering on any interface by using the spanni
ng-tree
bpdufilter enable interface configuration command without also enabling the Port Fast feature. This
command prevents the interface from sending or receiving BPDUs.
Caution Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in
spanning-tree loops.
You can enable the BPDU filtering feature for the entire switch or for an interface.
Understanding UplinkFast
Switches in hierarchical networks can be grouped into backbone switches, distribution switches, and
access switches. Figure 22-2 shows a complex network where distrib
ution switches and access switches
each have at least one redundant link that spanning tree blocks to prevent loops.

Cisco Catalyst 3750-X Specifications

General

Switching Capacity	160 Gbps
Stacking Bandwidth	64 Gbps
Max Stacking Units	9
Layer Support	Layer 2 and Layer 3
Form Factor	Rack-mountable
DRAM	256 MB
Flash Memory	64 MB
Model	Cisco Catalyst 3750-X Series
Ports	24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces	4 SFP or 2 SFP+
Features	StackWise Plus, EnergyWise
Image	IP Base or IP Services
Operating Temperature	0 to 40°C
Operating Humidity	10 to 85% noncondensing