CCNA 200-301 v1.1 reference — Network Access

STP protection features

PortFast, BPDU guard and BPDU filter, root guard and loop guard: what each protects and where to apply it.

Objective 2.5v1.1 exam target

STP protection features

Feature	Purpose	Apply to	Violation behavior
PortFast	Skip learning states — forward immediately	Edge ports (hosts, phones, servers)	n/a — speeds edge bring-up
BPDU guard	Shut the port down if any BPDU arrives	Edge ports with PortFast	err-disables the port
BPDU filter	Don't send BPDUs; ignore received ones	Edge ports (dangerous uplink misuse)	Port effectively leaves STP — loop risk
Root guard	Keep this port from becoming root port	Ports toward untrusted/downstream switches	Puts port in root-inconsistent (blocked) state until BPDUs stop
Loop guard	Block if BPDUs stop on a non-designated port	Redundant uplinks	Prevents a unidirectional link from opening a loop

The classic pairing is PortFast + BPDU guard on every edge port: the host comes up instantly, and any switch accidentally patched in produces a BPDU that err-disables the port before it can create a loop. Root guard belongs on ports where you must never accept a better root (toward other organizations' or untrusted switches); loop guard protects against unidirectional link failures where a port stops hearing BPDUs and could start forwarding.

Protect an edge port

Fast edge port with loop safety — Privileged EXEC → Interface configuration

Cisco IOS / IOS XE

configure terminal
interface gigabitethernet1/0/5
 switchport mode access
 spanning-tree portfast
 spanning-tree bpduguard enable
 end

Verify

show spanning-tree interface gi1/0/5 portfast
show running-config interface gi1/0/5
show interfaces status err-disabled

PortFast enabled on the port.
A BPDU-guard trip shows the port err-disabled — find the cause before re-enabling.

Global defaults exist: spanning-tree portfast default and spanning-tree portfast bpduguard default.
Never PortFast a link toward another switch.

Changes device configuration.

On this page

STP protection features
The classic pairing is PortFast + BPDU g…
Protect an edge port

Handbook sections

Related resources

Practise this topic Source topic 21: Spanning Tree Protocol (Part 2 & STP Toolkit)Practise topic 21 deck

Sources

Cisco CCNA 200-301 v1.1 Exam Topics (official PDF) — reviewed 2026-11-02
IEEE 802.1 Working Group — reviewed 2026-11-02
Cisco — LAN Switching Command Reference — reviewed 2026-11-02

Targets CCNA 200-301 v1.1 objectives. Supplemental blocks are labeled beyond exam scope.