Examkin

Network Access

400 soru

Tüm türler400Çoktan seçmeli204Çoklu seçim91Eşleştirme23Sıralama82
Soru 41Soru →

A network administrator needs to create a new VLAN named ENGINEERING (VLAN 40) on a Cisco Catalyst switch and assign interface FastEthernet 0/12 to this VLAN as an access port. Place the following Cisco IOS command sequence in the correct execution order from global configuration entry to final interface VLAN assignment.

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Cevap

The correct order of commands begins with entering global configuration mode (configure terminal), creating the VLAN (vlan 40), naming the VLAN (name ENGINEERING), navigating to the target interface (interface fastethernet 0/12), defining the interface as an access port (switchport mode access), and finally binding the interface to the specified VLAN (switchport access vlan 40).
The sequence follows the standard Cisco IOS configuration hierarchy. Global configuration mode must be established first to define the Layer 2 broadcast domain (vlan 40) and assign its optional descriptive name (name ENGINEERING). Next, configuration context shifts to the specific physical layer interface (interface fastethernet 0/12), where the operational mode is defined (switchport mode access) before binding the interface to the created access VLAN (switchport access vlan 40).

Adım Adım Çözüm

1
Enter global configuration mode.
The prompt changes to switch(config)#.
Global configuration mode is required to create VLAN definitions and navigate to interface configurations.
2
Execute 'vlan 40'.
The prompt changes to switch(config-vlan)#.
Creates VLAN 40 in the VLAN database and opens VLAN configuration sub-mode.
3
Execute 'name ENGINEERING'.
VLAN 40 is named ENGINEERING.
VLAN names must be configured while inside the config-vlan sub-mode.
4
Execute 'interface fastethernet 0/12'.
The prompt changes to switch(config-if)#.
Navigates directly to the specific interface configuration sub-mode for FastEthernet 0/12.
5
Execute 'switchport mode access'.
Interface FastEthernet 0/12 is statically configured as an access port.
Configuring access mode explicitly disables Dynamic Trunking Protocol (DTP) negotiation for trunking.
6
Execute 'switchport access vlan 40'.
Interface FastEthernet 0/12 is associated with VLAN 40.
Assigns untagged traffic on this access port to the target broadcast domain (VLAN 40).

Anahtar Kavram

Cisco IOS VLAN creation and interface access port configuration hierarchy
Soru 42Soru →

An engineer is configuring a wireless network for enterprise laptops using the Cisco Wireless LAN Controller (WLC) web interface. Under the Security tab, Layer 2 security is configured to use WPA2-Enterprise with 802.1X key management. Which sub-tab within the WLAN configuration page must be used to specify the external RADIUS authentication server for client authorization?

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Cevap: AAA Servers sub-tab under Security

Cevap

The RADIUS authentication server is assigned on the AAA Servers sub-tab under the Security tab of the WLAN configuration page.
On a Cisco WLC, after configuring Layer 2 Security for 802.1X (WPA2/WPA3 Enterprise), external RADIUS authentication servers are selected under the AAA Servers sub-tab located within the Security tab of the WLAN edit page.

Adım Adım Çözüm

1
Identify the WLAN configuration requirement
The scenario requires associating an 802.1X RADIUS authentication server with a newly defined WPA2-Enterprise WLAN.
When 802.1X is selected under Layer 2 Security, the WLC must know which external AAA server to forward EAP authentication requests to.
2
Locate the appropriate WLC GUI menu section
Navigate to WLANs > Edit > Security > AAA Servers.
Cisco WLC GUI categorizes external authentication server selection under the AAA Servers sub-tab within the Security tab.

Anahtar Kavram

WLC GUI WLAN RADIUS Authentication Server Configuration
Tahmini Süre:1m 0s
Soru 43Soru →

A enterprise network topology consists of three Cisco Catalyst switches (SwitchA, SwitchB, and SwitchC) interconnected in a redundant ring running Rapid PVST+ for VLAN 10. SwitchA is configured as the Root Bridge with a base priority of 4096. SwitchB has a base priority of 28672, and SwitchC has a base priority of 32768. All inter-switch links operate at 1 Gbps GigabitEthernet speeds (STP path cost = 4). SwitchC connects directly to SwitchA via interface GigabitEthernet0/1 and to SwitchB via interface GigabitEthernet0/2. Which Rapid PVST+ port role and state will interface GigabitEthernet0/2 assume on SwitchC for VLAN 10 after STP convergence completes?

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Cevap: Alternate port in the Discarding state

Cevap

Interface GigabitEthernet0/2 on SwitchC will become an Alternate port in the Discarding state.
SwitchC selects GigabitEthernet0/1 as its Root Port because its direct path to SwitchA has a cumulative path cost of 4, compared to a cost of 8 through SwitchB. For the link between SwitchB and SwitchC, both switches have an equal cost to the Root Bridge (4), so the switch with the lower Bridge ID (SwitchB at 28682 vs SwitchC at 32778) claims the Designated Port role. As a result, SwitchC's GigabitEthernet0/2 interface becomes an Alternate port and enters the Discarding state.

Adım Adım Çözüm

1
Calculate effective Bridge IDs including the System ID Extension (VLAN 10).
SwitchA BID = 4096 + 10 = 4106 (Root Bridge). SwitchB BID = 28672 + 10 = 28682. SwitchC BID = 32768 + 10 = 32778.
Rapid PVST+ appends the 12-bit VLAN ID to the base priority to form the bridge priority.
2
Evaluate root path costs for SwitchC to select its Root Port.
Path via Gi0/1 (direct to SwitchA) cost = 4. Path via Gi0/2 (to SwitchB to SwitchA) cost = 4 + 4 = 8. Gi0/1 becomes Root Port (Forwarding).
Each non-root switch selects the single port with the lowest cumulative cost toward the Root Bridge.
3
Determine Designated Port role on the segment between SwitchB and SwitchC.
Both SwitchB and SwitchC have a root path cost of 4 to SwitchA. SwitchB has a lower BID (28682) than SwitchC (32778), so SwitchB's interface becomes the Designated Port (Forwarding).
When root path costs on a segment are tied, the switch with the lowest Bridge ID wins the Designated Port role.
4
Assign the remaining port role for SwitchC's GigabitEthernet0/2 interface.
GigabitEthernet0/2 receives superior BPDUs from SwitchB and is assigned the Alternate port role in the Discarding state.
In Rapid PVST+ (802.1w), a port receiving BPDUs from another switch on a non-designated link serves as an Alternate port to provide a backup path to the root.

Anahtar Kavram

Rapid PVST+ Port Role and State Determination
Soru 44Soru →

A network administrator executes the following command on switch SW-Core1 to verify direct physical connections:

SW-Core1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID
SW-Access2 Gig 1/0/1 158 S I WS-C3850 Gig 1/0/24

Based on this output, which local physical interface on SW-Core1 is connected to the neighboring switch?

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Cevap: GigabitEthernet 1/0/1

Cevap

GigabitEthernet 1/0/1 is the local physical interface on SW-Core1 connected to the neighboring device.
The 'show cdp neighbors' command displays summary information about directly connected Cisco devices. The 'Local Intrfce' field specifies the local interface on the current device (SW-Core1) where the CDP frames are received, which is GigabitEthernet 1/0/1. The 'Port ID' field indicates the port on the neighboring device (GigabitEthernet 1/0/24).

Adım Adım Çözüm

1
Examine the output headers of the 'show cdp neighbors' command
Identify that 'Local Intrfce' corresponds to the local device interface, while 'Port ID' corresponds to the remote neighbor interface.
CDP separates local interface information from peer interface information across distinct table columns.
2
Locate the entry under the 'Local Intrfce' column for SW-Access2
The column value displays 'Gig 1/0/1'.
This confirms that SW-Core1 receives CDP advertisements from SW-Access2 on its local interface GigabitEthernet 1/0/1.

Anahtar Kavram

CDP Neighbor Table Data Fields Interpretation
Tahmini Süre:1m 0s
Soru 45Soru →

During a switch security audit on switch SW-1, a network engineer notices that interface FastEthernet0/10 is operating with default settings: its administrative mode is dynamic auto and it is assigned to default VLAN 1. The engineer needs to configure FastEthernet0/10 to statically connect an end-user workstation in VLAN 25 while explicitly disabling Dynamic Trunking Protocol (DTP) trunk negotiation on the interface.

Which combination of interface configuration commands correctly accomplishes this configuration?

Cevabı ve açıklamayı göster

Cevap: switchport mode access
switchport access vlan 25

Cevap

The command sequence consisting of 'switchport mode access' followed by 'switchport access vlan 25' correctly provisions the interface as a static access port in VLAN 25.
Executing 'switchport mode access' explicitly defines the interface as a Layer 2 access port, which automatically disables DTP trunk negotiation. Following this with 'switchport access vlan 25' places the interface into VLAN 25.

Adım Adım Çözüm

1
Enforce static access mode
Configuring 'switchport mode access' under interface configuration mode turns off dynamic trunking (DTP) negotiations toward becoming a trunk line and locks the port in access mode.
By default, Cisco switch ports run in dynamic auto mode, which allows them to negotiate trunking if the remote end initiates it.
2
Assign the access VLAN membership
Configuring 'switchport access vlan 25' assigns all untagged ingress traffic on this port to VLAN 25.
Access ports belong to exactly one data VLAN to isolate broadcast domains.

Anahtar Kavram

Configuring Layer 2 switch access ports and disabling DTP negotiation in Cisco IOS
Soru 46Soru →

A Cisco Catalyst switch interface configured as an 802.1Q trunk receives an incoming frame. Place the internal operational steps executed by the switch to process this frame into the correct chronological order from frame arrival to egress forwarding.

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Cevap

The correct sequence for 802.1Q ingress frame processing is: 1) Inspect header for TPID (0x8100), 2) Extract tagged VLAN ID or assign configured Native VLAN ID if untagged, 3) Verify VLAN against the allowed VLAN list (ingress filtering), 4) Update MAC address table for the VLAN domain, 5) Forward or flood the frame to egress ports in that VLAN.
The correct operational sequence begins when an ingress frame arrives on an 802.1Q trunk. The switch ASIC first checks for the 802.1Q TPID (0x8100). Next, it extracts the 12-bit VLAN ID from tagged frames or assigns the configured native VLAN ID to untagged frames. After determining the VLAN, the switch applies ingress filtering to verify if that VLAN ID is on the trunk's allowed VLAN list. If permitted, it updates its MAC address table associating the source MAC with that VLAN and ingress port, and finally makes the egress forwarding or flooding decision within that VLAN context.

Adım Adım Çözüm

1
Inspect the Ethernet header for 802.1Q encapsulation
Identifies if the frame contains a 4-byte 802.1Q header with EtherType 0x8100.
The switch must determine whether the frame is tagged before interpreting VLAN fields.
2
Derive the internal VLAN context
Extracts the 12-bit VID from the tag header, or maps untagged traffic to the native VLAN.
802.1Q rules dictate that untagged frames belong to the native VLAN, while tagged frames belong to their explicit VID.
3
Execute ingress VLAN pruning check (allowed list filtering)
Checks if the derived VLAN is permitted by the 'switchport trunk allowed vlan' configuration.
If the VLAN is pruned/disallowed, the switch drops the frame immediately prior to MAC table processing.
4
Learn source MAC address
Adds or updates the source MAC address entry in the CAM table for the derived VLAN context.
Dynamic MAC learning occurs per-VLAN after verifying ingress permission.
5
Perform egress forwarding decision
Forwards frame to egress destination interface(s) in the matching VLAN domain.
Layer 2 forwarding logic constrains broadcast and unicast traffic strictly within the matched VLAN boundary.

Anahtar Kavram

802.1Q Trunk Ingress Frame Processing Pipeline
Tahmini Süre:2m 0s
Soru 47Soru →

Match each Layer 2 discovery protocol attribute or configuration parameter on the left to its corresponding protocol or timer specification on the right.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Cisco proprietary protocol enabled globally by default on Cisco switch platforms
Vendor-neutral discovery protocol standardized under IEEE 802.1AB
Protocol default update frequency of 60 seconds with a holdtime of 180 seconds
Protocol default update frequency of 30 seconds with a holdtime of 120 seconds

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

The Cisco proprietary protocol matches Cisco Discovery Protocol (CDP). The IEEE 802.1AB standard matches Link Layer Discovery Protocol (LLDP). The 60-second update and 180-second holdtime match CDP Default Timers. The 30-second update and 120-second holdtime match LLDP Default Timers.
Each left-side item correctly correlates to its designated discovery protocol origin, governing IEEE specification, or default timer values.

Adım Adım Çözüm

1
Differentiate between proprietary and open standard Layer 2 discovery protocols.
Identify CDP as Cisco proprietary and LLDP as IEEE 802.1AB standard.
CDP operates exclusively on Cisco devices by default, whereas LLDP allows interoperability across heterogeneous vendor environments.
2
Compare default advertisement and holdtime timers for CDP and LLDP.
Map 60s update / 180s holdtime to CDP, and 30s update / 120s holdtime to LLDP.
CDP sends updates less frequently (60s) than LLDP (30s) under default Cisco IOS configurations.

Anahtar Kavram

Layer 2 Discovery Protocols (CDP vs LLDP standards, ownership, and default timers)
Soru 48Soru →

An administrator is configuring an IEEE 802.1Q trunk link between two Cisco Catalyst switches. By default, how does an IEEE 802.1Q trunk process Ethernet frames that belong to the configured native VLAN across the interswitch link?

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Cevap: It forwards frames belonging to the native VLAN untagged without inserting a 4-byte 802.1Q header.

Cevap

IEEE 802.1Q trunks forward Ethernet frames belonging to the native VLAN untagged without inserting a 4-byte 802.1Q tag header.
Under default IEEE 802.1Q operational mechanics, frames associated with the native VLAN are forwarded across interswitch trunk links in their original Ethernet format without an inserted 4-byte 802.1Q header tag. When the receiving switch accepts an untagged frame on its trunk port, it places that frame into its local native VLAN.

Adım Adım Çözüm

1
Identify the standard frame-handling behavior of IEEE 802.1Q trunking for native VLAN traffic.
IEEE 802.1Q specifies that traffic belonging to the designated native VLAN is transmitted across trunk links without a tag.
Transmitting native VLAN frames untagged allows backward compatibility with legacy switches or end-user devices that do not support VLAN tagging.
2
Compare native VLAN frame processing against tagged VLAN frame processing.
Non-native VLAN frames receive a 4-byte 802.1Q tag header, whereas native VLAN frames remain untagged.
The receiving switch inspects incoming frames on a trunk link; any frame lacking an 802.1Q tag is automatically assigned to the trunk port's configured native VLAN.

Anahtar Kavram

IEEE 802.1Q Native VLAN Untagged Traffic Handling
Soru 49Soru →

An enterprise network is deploying a centralized Cisco Wireless LAN Controller (WLC) solution based on the Split-MAC architecture. Which operational function is performed by the centralized WLC rather than the Lightweight Access Point (LAP)?

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Cevap: Processing 802.11 client authentication requests and translating 802.11 frames to 802.3 Ethernet frames

Cevap

Processing 802.11 client authentication requests and translating 802.11 frames to 802.3 Ethernet frames
Under Cisco's Split-MAC architecture, functions are split based on real-time sensitivity. Non-real-time management and control activities—such as processing client authentication, managing association states, and performing 802.11-to-802.3 frame translation—are handled centrally by the WLC.

Adım Adım Çözüm

1
Analyze the Split-MAC architecture concept.
Recognize that wireless MAC functions are divided into real-time functions (handled by the LAP) and non-real-time functions (handled by the WLC).
Split-MAC optimizes performance by handling time-sensitive 802.11 tasks locally on the AP while centralizing management and higher-layer processing on the WLC.
2
Categorize the responsibilities of the Lightweight Access Point (LAP).
LAPs handle transmission of beacons, probe responses, immediate MAC layer acknowledgments (ACKs), RTS/CTS frame exchanges, and power-save buffering.
These tasks require immediate radio-level responses and cannot tolerate CAPWAP tunnel latency to a remote controller.
3
Categorize the responsibilities of the Wireless LAN Controller (WLC).
The WLC handles non-real-time management, 802.11 authentication/association, 802.1X/EAP processing, Radio Resource Management (RRM), and 802.11 to 802.3 frame translation.
Centralizing these functions allows uniform security policy enforcement and seamless mobility across the network.

Anahtar Kavram

Split-MAC Architecture Functional Division
Tahmini Süre:1m 0s
Soru 50Soru →

A network administrator needs to manually configure interface GigabitEthernet1/0/22 on a Cisco Catalyst switch as a dedicated access port for a workstation in VLAN 35 (FINANCE). Assuming VLAN 35 already exists in the VLAN database, which set of commands must be applied under the interface configuration mode to properly complete this task?

Cevabı ve açıklamayı göster

Cevap: switchport mode access
switchport access vlan 35

Cevap

To configure a switch interface as a static access port in VLAN 35, the engineer must enter interface configuration mode and execute 'switchport mode access' followed by 'switchport access vlan 35'.
The correct command sequence requires defining the interface operational type as an access port using 'switchport mode access' and then binding the port to the specific VLAN ID using 'switchport access vlan 35'.

Adım Adım Çözüm

1
Enter interface configuration mode
Navigates to the interface context using 'interface GigabitEthernet1/0/22'.
Configuration commands for port membership must be executed under the specific interface prompt.
2
Set administrative mode to access
Executes 'switchport mode access'.
Definitive host access operation disables DTP dynamic negotiation into trunking state.
3
Assign the access VLAN ID
Executes 'switchport access vlan 35'.
Maps untagged ingress frames from the connected device into VLAN 35.

Anahtar Kavram

Cisco IOS Access Port Assignment Syntax
Soru 51Soru →

Two Cisco Catalyst switches, SW1 and SW2, are connected via their GigabitEthernet0/1 interfaces. SW1 is configured with `switchport mode dynamic desirable` and `switchport trunk native vlan 99`. SW2 is configured with `switchport mode dynamic auto` and retains its default native VLAN 1. Assuming default IEEE 802.1Q trunking behavior, what is the resulting operational state of this interswitch link?

Cevabı ve açıklamayı göster

Cevap: A trunking operational mode is successfully established via DTP negotiation, but PVST+ places VLAN 1 and VLAN 99 into a blocking state on the link due to a PVID inconsistency.

Cevap

A trunking operational mode is successfully established via DTP negotiation, but PVST+ places VLAN 1 and VLAN 99 into a blocking state on the link due to a PVID inconsistency.
Dynamic Trunking Protocol (DTP) operates independently of native VLAN configurations, allowing a port in dynamic desirable mode to successfully negotiate an operational 802.1Q trunk with a port in dynamic auto mode. However, Cisco PVST+ sends Spanning Tree BPDUs with VLAN tagging metadata (SSTP). When the switches receive BPDUs indicating different native VLAN IDs (VLAN 99 vs VLAN 1), PVST+ flags a PVID inconsistency and places VLAN 1 and VLAN 99 into a blocking state on the interface to prevent unauthorized cross-VLAN data leakage and loops.

Adım Adım Çözüm

1
Analyze DTP mode negotiation between SW1 and SW2
SW1 (`dynamic desirable`) actively sends DTP frames to SW2 (`dynamic auto`), negotiating the link into an operational 802.1Q trunk.
DTP negotiation only evaluates DTP operational modes and encapsulation settings, not native VLAN IDs.
2
Evaluate Native VLAN configuration parameter compatibility
SW1 uses Native VLAN 99, while SW2 uses Native VLAN 1, creating a native VLAN mismatch across the trunk.
Untagged frames sent from VLAN 99 on SW1 would arrive on SW2 and be incorrectly ingested into VLAN 1.
3
Determine Spanning Tree Protocol (PVST+) operational behavior
PVST+ detects the Port VLAN ID (PVID) mismatch using Cisco Shared Spanning Tree Protocol (SSTP) BPDUs and places VLAN 1 and VLAN 99 into a `PVID-inc` (blocking) state on GigabitEthernet0/1.
Blocking the mismatched native VLANs prevents potential Layer 2 loops and cross-VLAN traffic leakage while allowing other matching VLANs to continue forwarding normally.

Anahtar Kavram

802.1Q Native VLAN Mismatch and PVST+ PVID Inconsistency Protection
Tahmini Süre:2m 0s
Soru 52Soru →

An administrator is configuring a corporate WLAN on a Cisco Wireless LAN Controller (WLC) GUI for enterprise clients requiring 802.1X authentication and centralized CAPWAP traffic forwarding. During initial client association tests, clients fail to complete 802.1X authentication and fail to receive an IP address via DHCP. Inspection of the WLC GUI shows that the WLAN status is enabled, but client traffic is mapped to the default management interface, and no authentication server is processing client login requests for this WLAN. Which TWO configurations within the WLC GUI WLAN edit menu must be applied to resolve these client connectivity issues? (Select two.)

Geçerli olan tümünü seçin

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Cevap: Navigate to WLANs > Edit > Security > AAA Servers tab and select the active RADIUS server under Server 1 in the Authentication Servers section.; Navigate to WLANs > Edit > General tab and change the Interface/Interface Group dropdown from management to the mapped dynamic client VLAN interface.

Cevap

To resolve 802.1X client authentication failure and improper DHCP address assignment, the administrator must select an active RADIUS server under the Security > AAA Servers tab and reassign the WLAN interface mapping from management to the client dynamic VLAN interface under the General tab.
In the Cisco WLC GUI, establishing functional client connectivity for an 802.1X enterprise WLAN requires configuring AAA authentication server bindings under WLANs > Edit > Security > AAA Servers. Additionally, assigning client traffic to the correct dynamic interface corresponding to the client VLAN must be performed under the WLANs > Edit > General tab.

Adım Adım Çözüm

1
Diagnose 802.1X RADIUS server assignment failure
Identify that 802.1X authentication requests are dropped because no RADIUS server is bound to the WLAN under WLANs > Edit > Security > AAA Servers.
WLC WLANs configured for WPA2/WPA3-Enterprise (802.1X) require an explicit AAA server mapping in the WLAN settings to pass EAP messages to RADIUS.
2
Diagnose client VLAN and DHCP failure
Identify that mapping client traffic to the management interface prevents clients from obtaining lease addresses on the designated client subnet.
Cisco WLC GUI requires mapping each WLAN to its corresponding dynamic interface on the General tab to ensure proper VLAN tagging and DHCP relay forwarding.

Anahtar Kavram

WLAN Interface Mapping and AAA Server Association in Cisco WLC GUI
Soru 53Soru →

A network administrator is troubleshooting interswitch trunking between SW-Core1 and SW-Access1. The administrator issues the `show interfaces trunk` command on SW-Core1 and observes the following output:

PortModeEncapsulationStatusNative vlan
Gi0/24on802.1qtrunking10
PortVlans allowed on trunk
Gi0/241-4094
PortVlans allowed and active in management domain
Gi0/241,10,20,30
PortVlans in spanning tree forwarding state and not pruned
Gi0/241,10,30

Users in VLAN 20 connected to SW-Access1 report complete loss of connectivity to resources in VLAN 20 connected to SW-Core1, whereas users in VLAN 10 and VLAN 30 report normal operation. Based on the command output, what is the cause of the communication failure for VLAN 20?

Cevabı ve açıklamayı göster

Cevap: VLAN 20 is not in the Spanning Tree Protocol forwarding state (or has been pruned) on interface GigabitEthernet0/24.

Cevap

VLAN 20 is missing from the Spanning Tree Protocol forwarding state list on the trunk interface, preventing frames in VLAN 20 from being forwarded across the link.
The correct answer identifies that VLAN 20 is absent from the final section of the output: 'Vlans in spanning tree forwarding state and not pruned'. For traffic to pass across an 802.1Q trunk, a VLAN must be allowed on the trunk, active in the VLAN database, and in the STP forwarding state.

Adım Adım Çözüm

1
Analyze the 'Vlans allowed on trunk' field in the CLI output.
Interface GigabitEthernet0/24 allows VLANs 1-4094, meaning no explicit manual pruning (`switchport trunk allowed vlan`) is blocking VLAN 20.
Verifies that trunk port configuration permits VLAN 20 traffic.
2
Analyze the 'Vlans allowed and active in management domain' field.
VLAN 20 is listed alongside VLAN 1, 10, and 30, confirming VLAN 20 exists in the local VLAN database and is active.
Rules out local VLAN creation or state issues on SW-Core1.
3
Compare active management VLANs against 'Vlans in spanning tree forwarding state and not pruned'.
VLANs 1, 10, and 30 are forwarding, but VLAN 20 is absent from this list.
If a VLAN is missing from the final STP forwarding section, traffic for that VLAN is either blocked by STP or dynamic VTP pruning, preventing frame transmission across the link.

Anahtar Kavram

802.1Q Trunk Operational Verification and STP Per-VLAN Forwarding States
Tahmini Süre:1m 30s
Soru 54Soru →

A newly deployed workstation experiences network initial connection timeouts and fails to receive an IPv4 address allocation from the DHCP server upon booting up. A technician notes that the switch interface connected to the workstation takes 30 seconds to begin forwarding traffic due to standard 802.1D Spanning Tree Protocol (STP) state transitions. Which configuration change on the access interface resolves this issue, and what is its exact operational behavior?

Cevabı ve açıklamayı göster

Cevap: Enable PortFast on the access interface, allowing it to bypass the Listening and Learning states and transition immediately from Blocking to Forwarding.

Cevap

Enabling PortFast on the host access interface immediately transitions the port from Blocking to Forwarding by bypassing the 15-second Listening and 15-second Learning STP states.
Standard 802.1D STP transitions ports through Blocking, Listening (15s), and Learning (15s) states before entering Forwarding. On edge access ports connected to workstations, this 30-second delay causes DHCP requests to time out. Enabling PortFast allows the switch interface to transition immediately from Blocking to Forwarding, bypassing Listening and Learning states.

Adım Adım Çözüm

1
Identify the cause of the delay during host boot-up.
Standard IEEE 802.1D STP requires a port to spend 15 seconds in the Listening state and 15 seconds in the Learning state (total 30 seconds) before reaching Forwarding.
During this 30-second delay, the switch drops user data frames, causing host applications (such as DHCP client requests) to time out.
2
Determine the appropriate Cisco STP optimization feature for access ports connected to end devices.
Cisco PortFast is designed specifically for access ports connected directly to workstations, servers, or end-user hosts.
PortFast bypasses the Listening and Learning states, allowing the interface to transition directly from Blocking to Forwarding upon link up.

Anahtar Kavram

Cisco STP PortFast operation and state bypass mechanism
Tahmini Süre:1m 0s
Soru 55Soru →

A network administrator needs to create VLAN 85 named GUESTS on a Cisco Catalyst switch and configure interface GigabitEthernet0/2 as a static access port assigned to this VLAN, starting from Privileged EXEC mode (`Switch#`). In what sequence should the administrator execute the required Cisco IOS commands?

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct configuration order starts in Privileged EXEC mode with 'configure terminal', followed by 'vlan 85', 'name GUESTS', 'interface GigabitEthernet0/2', 'switchport mode access', and finally 'switchport access vlan 85'.
To successfully create a VLAN and configure an access port in Cisco IOS, commands must be executed in a specific hierarchical sequence. Starting at Privileged EXEC mode (`Switch#`), the user enters Global Configuration mode (`Switch(config)#`) using `configure terminal`. Next, VLAN 85 is instantiated with `vlan 85` into VLAN configuration mode (`Switch(config-vlan)#`), where `name GUESTS` sets the label. Moving back to Global Configuration mode context to select the target interface via `interface GigabitEthernet0/2` places the user in Interface Configuration mode (`Switch(config-if)#`). Here, `switchport mode access` disables dynamic trunk negotiation, and `switchport access vlan 85` assigns the port to the intended broadcast domain.

Adım Adım Çözüm

1
Enter Global Configuration mode from Privileged EXEC mode.
Prompt changes to `Switch(config)#` after running `configure terminal`.
Global configuration mode is required to initiate VLAN creation and interface selection commands.
2
Create VLAN 85.
Prompt changes to `Switch(config-vlan)#` after issuing `vlan 85`.
Creates the VLAN ID in the Layer 2 database and opens VLAN configuration submode.
3
Assign the name GUESTS to the VLAN.
VLAN 85 is labeled with the name GUESTS upon executing `name GUESTS`.
Name configuration must take place inside the VLAN configuration submode.
4
Select interface GigabitEthernet0/2 for editing.
Prompt changes to `Switch(config-if)#` after issuing `interface GigabitEthernet0/2`.
Moves the CLI context into interface configuration mode for the specified target interface.
5
Set the administrative mode of the port to static access mode.
The port mode changes from dynamic negotiation to explicit access mode via `switchport mode access`.
Statically defining access mode ensures DTP negotiation does not form a trunk link unintentionally.
6
Assign the interface to VLAN 85.
Traffic on GigabitEthernet0/2 is tagged internally for VLAN 85 using `switchport access vlan 85`.
Associates untagged frames received on this access port with VLAN 85.

Anahtar Kavram

Cisco IOS CLI hierarchy for VLAN definition and static access port assignment
Tahmini Süre:1m 30s
Soru 56Soru →

An administrator connects a workstation to a Cisco Catalyst switch interface configured with standard IEEE 802.1D Spanning Tree Protocol (STP) where PortFast has NOT been enabled. Arrange the operational steps and port state transitions in the correct chronological sequence from the moment physical link status changes to up until the spanning-tree topology update process completes.

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Cevap

The correct chronological sequence for standard 802.1D STP port activation without PortFast is: 1) Initializing in the Blocking state to inspect incoming BPDUs; 2) Transitioning to the Listening state (15s) to elect spanning-tree roles via BPDU exchange without MAC learning; 3) Transitioning to the Learning state (15s) after the first Forward Delay to populate MAC address table entries; 4) Transitioning to the Forwarding state after the second Forward Delay to process user data frames; 5) Transmitting a Topology Change Notification (TCN) BPDU toward the Root Bridge due to the non-PortFast state transition.
The correct order reflects standard 802.1D STP convergence behavior: Blocking -> Listening (15s role election) -> Learning (15s MAC table population) -> Forwarding (active data transfer) -> TCN generation. Disabling or omitting PortFast on an access interface causes the full 30-second convergence delay and forces a network-wide MAC address table aging timer reduction via TCN BPDUs.

Adım Adım Çözüm

1
Determine initial port state upon link initialization.
The port initializes in the Blocking state, dropping ingress traffic while listening for BPDUs.
Preventing layer 2 switching loops requires keeping the port from forwarding broadcast or unicast traffic prior to topology calculation.
2
Trace the first state transition during spanning-tree role determination.
The port enters the Listening state for 15 seconds (Forward Delay), sending and receiving BPDUs.
During Listening, the switch determines whether the port will become a Root Port, Designated Port, or return to Blocking, but does not learn MAC addresses.
3
Trace the second state transition following the first Forward Delay expiration.
The port transitions to the Learning state for 15 seconds (Forward Delay), inspecting frame source MAC addresses to populate the CAM table.
Learning MAC address locations prior to active frame forwarding minimizes unicast flooding once data transmission begins.
4
Identify the active operational state reached after timer expiration.
The port transitions to the Forwarding state, enabling bi-directional user payload frame transmission.
After passing two full Forward Delay timers (30 seconds total), the interface is confirmed loop-free and fully operational.
5
Determine post-transition notification behavior for non-PortFast ports.
The switch transmits a Topology Change Notification (TCN) BPDU out its Root Port toward the Root Bridge.
Because PortFast is not configured, transitioning a port to Forwarding triggers a topology change event, instructing switches in the domain to reduce MAC aging timers from 300 seconds to the Forward Delay timer (15 seconds).

Anahtar Kavram

IEEE 802.1D STP Port State Convergence Sequence and TCN Generation
Soru 57Soru →

A network administrator is establishing link aggregation between a Cisco AireOS Wireless LAN Controller (WLC) and an upstream Cisco Catalyst switch to increase bandwidth and provide interface redundancy. The administrator configures ports GigabitEthernet 1/0/1 through 1/0/4 on the Catalyst switch using the command 'channel-group 10 mode active' and enables LAG on the WLC. However, after the WLC reboots, the EtherChannel fails to negotiate successfully. Which condition is causing this link aggregation failure?

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Cevap: The upstream switch ports are configured for dynamic LACP negotiation, but Cisco AireOS WLCs only support static EtherChannel bundles configured with mode on.

Cevap

The upstream switch ports are configured for dynamic LACP negotiation, but Cisco AireOS WLCs only support static EtherChannel bundles configured with mode on.
Cisco AireOS Wireless LAN Controllers require all connected distribution system ports to be bundled into a single static EtherChannel. Because AireOS does not support LACP (IEEE 802.3ad) or PAgP negotiation protocols, the upstream switch interfaces must be configured with 'mode on'. When the switch ports are configured with 'mode active', the switch expects LACP packets that the AireOS controller never sends, preventing the link aggregation bundle from establishing.

Adım Adım Çözüm

1
Identify the protocol support for Link Aggregation (LAG) on Cisco AireOS Wireless LAN Controllers.
AireOS controllers do not support dynamic EtherChannel negotiation protocols such as LACP or PAgP.
LAG on AireOS bundles all physical distribution system ports into a single logical channel that requires unconditional static bundling on the connected switch.
2
Evaluate the switch port configuration command 'channel-group 10 mode active'.
The 'mode active' keyword enables LACP dynamic negotiation on the Catalyst switch ports.
Because the WLC will not transmit or respond to LACP control packets, the switch ports remain in an unbundled or suspended state waiting for LACP negotiation.
3
Determine the necessary configuration change on the switch interfaces.
Change the switch port channel command to 'channel-group 10 mode on'.
Configuring 'mode on' forces the switch ports into a static EtherChannel without attempting LACP or PAgP negotiation, matching the WLC requirements.

Anahtar Kavram

Cisco AireOS WLC Link Aggregation (LAG) EtherChannel Mode Requirements
Soru 58Soru →

An engineer connects two Cisco Catalyst switches using their GigabitEthernet0/1 interfaces. Interface GigabitEthernet0/1 on Switch-1 is configured with `switchport mode dynamic auto`. Interface GigabitEthernet0/1 on Switch-2 is configured with `switchport mode trunk` followed by `switchport nonegotiate`. What is the resulting operational state of the GigabitEthernet0/1 interface on Switch-1?

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Cevap: It operates as an access port because dynamic trunking negotiation frames are suppressed by Switch-2.

Cevap

The interface on Switch-1 operates as an access port because dynamic trunking negotiation frames are suppressed by Switch-2.
When an interface is in dynamic auto mode, it does not initiate DTP negotiation; it only responds to incoming DTP frames. Since the remote switch interface is configured with 'switchport nonegotiate', no DTP packets are sent across the link. Consequently, the local interface remains in its default access operational state.

Adım Adım Çözüm

1
Analyze Switch-1 DTP configuration
Switch-1 is configured as 'dynamic auto', meaning it will operate as an access port unless it actively receives DTP desirable or trunk negotiation frames.
Ports in dynamic auto mode wait passively for DTP proposals from the neighboring switch.
2
Analyze Switch-2 DTP configuration
Switch-2 has 'switchport nonegotiate' applied, which completely stops the interface from transmitting DTP frames.
The 'switchport nonegotiate' command disables DTP frame generation on static trunk or access ports.
3
Determine the resulting link operational state on Switch-1
Because Switch-1 receives no DTP negotiation frames, it never transitions to trunk mode and remains operating as an access port.
Without receiving incoming DTP frames, a dynamic auto interface defaults to operational access mode.

Anahtar Kavram

DTP Mode Negotiation and Nonegotiate Behavior
Soru 59Soru →

Two Cisco Catalyst switches, SwitchA and SwitchB, are connected via their GigabitEthernet0/1 interfaces. SwitchA is configured with the commands `switchport mode dynamic desirable` and `switchport trunk native vlan 20`. SwitchB is configured with `switchport mode dynamic auto` and default interface settings (`switchport trunk native vlan 1`). Based on this operational configuration, which statement correctly describes the trunking state and frame handling across this link?

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Cevap: The link successfully negotiates an 802.1Q trunk, but untagged frames sent from SwitchA's native VLAN 20 will be processed in VLAN 1 on SwitchB, causing a cross-VLAN traffic leak and triggering CDP error logs.

Cevap

The link successfully negotiates an 802.1Q trunk, but untagged frames sent from SwitchA's native VLAN 20 will be processed in VLAN 1 on SwitchB, causing a cross-VLAN traffic leak and triggering CDP error logs.
The combination of dynamic desirable on one side and dynamic auto on the other successfully forms an 802.1Q trunk via Dynamic Trunking Protocol. Because native VLAN traffic is sent untagged by default under 802.1Q, frames originating in VLAN 20 on the first switch are received untagged on the second switch and mapped to its native VLAN 1. This creates a cross-VLAN leak and causes Cisco Discovery Protocol to log warning messages regarding the native VLAN mismatch.

Adım Adım Çözüm

1
Evaluate DTP negotiation between SwitchA and SwitchB.
SwitchA is set to dynamic desirable (actively seeking to form a trunk) and SwitchB is set to dynamic auto (willing to form a trunk if requested). This combination successfully negotiates an operational trunk link.
DTP operational mode matrix dictates that desirable + auto results in a trunking state.
2
Analyze 802.1Q native VLAN tagging mechanics across the trunk.
SwitchA sends VLAN 20 traffic without an 802.1Q tag. When SwitchB receives untagged traffic on a trunk port, it forwards that traffic to its own configured native VLAN (VLAN 1).
By default, 802.1Q trunks transmit native VLAN frames without inserting a 4-byte VLAN tag header.
3
Determine control plane diagnostic behavior.
CDP exchanges native VLAN information via TLVs and generates console log warnings about the native VLAN mismatch, but traffic forwarding continues and the interface remains up/up.
CDP provides notification of misconfigurations but does not automatically shut down interfaces or block native VLAN traffic unless explicitly combined with STP loop guard/BPDU guard mechanisms.

Anahtar Kavram

802.1Q Native VLAN Tagging Mechanics and DTP Negotiation
Tahmini Süre:2m 0s
Soru 60Soru →

A network administrator needs to manually configure an 802.1Q trunk on switch port GigabitEthernet0/1 and assign VLAN 99 as the untagged native VLAN. Place the Cisco IOS CLI configuration commands in the correct sequential order required to accomplish this task.

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Cevabı ve açıklamayı göster

Cevap

The correct order of configuration commands is: enter interface context ('interface GigabitEthernet0/1'), specify 802.1Q encapsulation ('switchport trunk encapsulation dot1q'), set operational mode to trunk ('switchport mode trunk'), and set native VLAN 99 ('switchport trunk native vlan 99').
To successfully establish an 802.1Q trunk link with a custom native VLAN on a Cisco switch interface, commands must be entered in hierarchical CLI order: first select the targeted interface ('interface GigabitEthernet0/1'), define the trunk encapsulation standard ('switchport trunk encapsulation dot1q'), force the link into trunking mode ('switchport mode trunk'), and finally designate the untagged native VLAN ('switchport trunk native vlan 99').

Adım Adım Çözüm

1
Navigate to the targeted physical interface context.
Switch enters interface configuration mode for GigabitEthernet0/1.
Trunk configuration commands are applied directly under the specific switchport interface context.
2
Set the trunk encapsulation type to 802.1Q.
The interface uses 802.1Q frame tagging for VLAN multiplexing.
On Cisco Catalyst switches supporting legacy ISL and 802.1Q, encapsulation type must be explicitly specified before enabling trunk mode.
3
Enable static trunking mode.
The port transitions to a permanent 802.1Q trunking operational state.
The command 'switchport mode trunk' forces the interface into trunking mode.
4
Configure the native VLAN assignment.
VLAN 99 is assigned as the native (untagged) VLAN on the trunk.
Untagged frames sent and received over the 802.1Q trunk will be mapped to VLAN 99.

Anahtar Kavram

IEEE 802.1Q Trunk CLI Configuration Sequence
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