Cisco Catalyst 2960-X Command Reference

spanning-tree guard
To enable or disable root-guard mode or loop-guard mode on the VLANs associated with an interface, use
the spanning-tree guard command in interface configuration mode. To return to the default settings, use the
no form of this command.
spanning-tree guard {loop| root| none}
no spanning-tree guard
Syntax Description
Enables the loop-guard mode on the interface.loop
Enables root-guard mode on the interface.root
Sets the guard mode to none.none
Command Default
Root-guard mode is disabled.
Loop-guard mode is configured according to the spanning-tree loopguard default command in global
configuration mode.
Command Modes
Interface configuration
Command History
ModificationRelease
This command was introduced.Cisco IOS 15.0(2)EX
Usage Guidelines
You can enable root guard or loop guard when the switch is operating in the per-VLAN spanning-tree plus
(PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.
You cannot enable both root guard and loop guard at the same time.
Use the spanning-tree guard loop command to override the setting of the spanning-tree loop guard default
setting.
When root guard is enabled, if spanning-tree calculations cause an interface to be selected as the root port,
the interface transitions to the root-inconsistent (blocked) state to prevent the switch from becoming the root
switch or from being in the path to the root. The root port provides the best path from the switch to the root
switch.
When the no spanning-tree guard or theno spanning-tree guard none command is entered, root guard is
disabled for all VLANs on the selected interface. If this interface is in the root-inconsistent (blocked) state,
it automatically transitions to the listening state.
Catalyst 2960-X Switch Layer 2 Command Reference, Cisco IOS Release 15.0(2)EX
86 OL-29043 -01
Layer 2 Commands
spanning-tree guard

Cisco Catalyst 2960-X Specifications

General

Console port	RJ-45
USB 2.0 ports quantity	2
SFP module slots quantity	4
Installed SFP modules quantity	-
Gigabit Ethernet (copper) ports quantity	48
Basic switching RJ-45 Ethernet ports type	Gigabit Ethernet (10/100/1000)
Power source	AC
Input current	5 A
AC input voltage	100 - 240 V
Power consumption (typical)	60.9 W
Number of power supply units	1
Redundant power supply (RPS) support	Yes
Operating altitude	0 - 3000 m
Non-operating altitude	0 - 4000 m
Storage temperature (T-T)	-25 - 70 °C
Operating temperature (T-T)	-5 - 40 °C
Operating relative humidity (H-H)	10 - 95 %
Switching protocols	UDP, TCP, RADIUS/TACACS+
Number of VLANs	1023
Networking standards	IEEE 802.1ab, IEEE 802.1D, IEEE 802.1p, IEEE 802.1Q, IEEE 802.1s, IEEE 802.1w, IEEE 802.1x, IEEE 802.3, IEEE 802.3ab, IEEE 802.3ad, IEEE 802.3ae, IEEE 802.3af, IEEE 802.3ah, IEEE 802.3at, IEEE 802.3az, IEEE 802.3u, IEEE 802.3x, IEEE 802.3z
Throughput	107.1 Mpps
Jumbo frames	9216
Number of queues	8
MAC address table	16000 entries
Number of static routes	1000
DHCP features	DHCP server
Authentication	MAC-based authentication, Port-based authentication
Security algorithms	802.1x RADIUS, SNMP, SSH
Access Control List (ACL) rules	3
Switch type	Managed
Switch layer	L2/L3
Safety	UL 60950-1, CAN/CSA-C22.2 No. 60950-1, EN 60950-1, IEC 60950-1, AS/NZS 60950-1
Form factor	1U
Product color	Black
Total Power over Ethernet (PoE) budget	370 W
Power over Ethernet (PoE) ports quantity	24
Power over Ethernet plus (PoE+) ports quantity	12
Memory type	DRAM
Noise level	39 dB
Flash memory	128 MB
Internal memory	512 MB
Processor frequency	600 MHz
Mean time between failures (MTBF)	276870 h

Weight and Dimensions

Depth	368 mm
Width	445 mm
Height	45 mm
Weight	5800 g