Examkin

L2 Switching Concepts and MAC Table Operation

28 soru

Tüm türler28Çoktan seçmeli14Çoklu seçim7Sıralama7
Soru 1Soru →

Host A sends an Ethernet frame addressed to Host B into port FastEthernet0/1 of a Layer 2 switch. The switch MAC address table already contains an entry for Host B on port FastEthernet0/2, but has no prior entry for Host A. What action does the switch take upon receiving this frame?

Cevabı ve açıklamayı göster

Cevap: Learns Host A's MAC address on port FastEthernet0/1 and forwards the frame directly out port FastEthernet0/2.

Cevap

The switch records Host A's MAC address on FastEthernet0/1 and forwards the frame exclusively out FastEthernet0/2.
When a switch receives a frame, it always inspects the source MAC address to update its MAC table (learning Host A on FastEthernet0/1). It then checks the destination MAC address; since Host B is already recorded on FastEthernet0/2, the switch forwards the frame exclusively out that destination port.

Adım Adım Çözüm

1
Examine the ingress frame's source MAC address
Host A's MAC address is learned and added to the MAC address table associated with port FastEthernet0/1.
Layer 2 switches dynamically populate their MAC address tables by inspecting incoming frame source MAC addresses and ingress port numbers.
2
Examine the ingress frame's destination MAC address
Host B's MAC address is found in the table associated with port FastEthernet0/2.
If the destination MAC address is already present in the MAC address table, the switch performs point-to-point known unicast forwarding.
3
Forward the frame
The frame is transmitted solely out port FastEthernet0/2.
Known unicast destination entries prevent unnecessary frame flooding across other switch ports.

Anahtar Kavram

Layer 2 MAC Address Table Learning and Forwarding Logic
Soru 2Soru →

A Layer 2 switch receives an Ethernet frame with a unicast destination MAC address that does not currently exist in its MAC address table. Which two actions does the switch take upon receiving this frame?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: It floods the frame out all active interfaces in the VLAN except the ingress port.; It examines the source MAC address of the frame and updates its MAC address table if the entry is missing.

Cevap

The switch populates its MAC address table using the ingress frame's source MAC address and floods the frame out all active switch ports within the VLAN, excluding the port on which the frame arrived.
When a Layer 2 switch receives a frame, it always inspects the source MAC address to learn or update its location in the MAC address table. If the destination MAC address is unknown, the switch performs an unknown unicast flood by forwarding the frame to all active interfaces in the VLAN, except the port on which the frame was received.

Adım Adım Çözüm

1
Inspect the incoming Ethernet frame header.
The switch identifies the frame's source MAC address and destination MAC address.
Learning and forwarding decisions are based on Layer 2 MAC addresses.
2
Process the source MAC address for learning.
The source MAC address is mapped to the ingress switch port in the MAC address table.
The MAC address table populates dynamically from incoming traffic source addresses.
3
Determine forwarding action based on destination MAC address lookup.
Since the destination MAC address is not found in the table, the frame is classified as unknown unicast and flooded out all ports except the receiving port.
Flooding ensures the frame reaches its intended destination even if its switch port location is currently unknown.

Anahtar Kavram

Switch learning mechanics and unknown unicast flooding
Soru 3Soru →

An Ethernet frame with a destination MAC address of FFFF.FFFF.FFFF arrives on switch port FastEthernet0/5. The switch MAC address table currently contains no entry for the source MAC address of the frame. Which dual action will the switch perform upon receiving this frame?

Cevabı ve açıklamayı göster

Cevap: Record the source MAC address mapped to FastEthernet0/5 in the MAC table, and flood the frame out all active switch ports except FastEthernet0/5.

Cevap

Record the source MAC address mapped to FastEthernet0/5 in the MAC table, and flood the frame out all active switch ports except FastEthernet0/5.
When a Layer 2 switch receives an Ethernet frame, it first inspects the source MAC address. If the source MAC is not present in the MAC table, the switch creates a new entry mapping that source MAC address to the receiving port (FastEthernet0/5). Next, it inspects the destination MAC address. Because FFFF.FFFF.FFFF is the Layer 2 broadcast address, the switch floods the frame out every active interface in the VLAN except the interface on which the frame arrived.

Adım Adım Çözüm

1
Examine the incoming frame's source MAC address and ingress port.
The switch notes that the source MAC address is not currently in the MAC address table.
Layer 2 switches perform MAC learning by recording the incoming source MAC address associated with the ingress interface (FastEthernet0/5).
2
Examine the incoming frame's destination MAC address.
The destination MAC address is identified as FFFF.FFFF.FFFF (Layer 2 broadcast).
Broadcast frames are intended for all devices within the broadcast domain.
3
Execute frame forwarding.
The frame is flooded out all operational ports belonging to the same VLAN, excluding the receiving port (FastEthernet0/5).
Flooding ensures all hosts receive the broadcast, while excluding the ingress port prevents frame loops.

Anahtar Kavram

Layer 2 MAC Address Table Learning and Broadcast Frame Flooding Logic
Soru 4Soru →

A Cisco Catalyst switch receives an Ethernet frame on interface FastEthernet0/1. The frame contains a source MAC address that does not currently exist in the MAC address table, and a destination MAC address that is already registered to interface FastEthernet0/4. In what correct sequential order does the switch perform its internal frame processing and forwarding tasks?

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

1. Receive the Ethernet frame on interface FastEthernet0/1 and inspect the Layer 2 header for source and destination MAC addresses.
2. Check the MAC address table for the source MAC address and create a dynamic entry associating it with FastEthernet0/1.
3. Perform a lookup in the MAC address table using the destination MAC address to identify the associated egress port.
4. Forward the unicast frame exclusively out interface FastEthernet0/4 without flooding.
When a switch receives a frame, it sequentially executes two main phases: MAC learning followed by frame forwarding. First, it extracts the header information on the ingress port. Second, it inspects the source MAC address; if missing from the MAC address table, it records a dynamic entry associating the source MAC with the receiving port and VLAN. Third, it checks the destination MAC address against its MAC address table. Fourth, because a matching entry exists for FastEthernet0/4, the switch forwards the frame directly out that single interface without flooding.

Adım Adım Çözüm

1
Frame Ingress Inspection
Source and destination MAC address fields are read from the incoming Ethernet frame header.
The switch must inspect the frame header on port FastEthernet0/1 to extract the Layer 2 addressing information.
2
Source MAC Learning
A new entry is added to the MAC address table mapping the source MAC address to interface FastEthernet0/1.
Layer 2 switches learn source MAC addresses upon ingress prior to making any forwarding decisions.
3
Destination Address Table Query
The destination MAC address is matched to existing entry for interface FastEthernet0/4.
The switch inspects its Content Addressable Memory (CAM) table to determine where to direct the frame.
4
Known Unicast Egress Forwarding
The frame is transmitted directly out interface FastEthernet0/4.
Matching a known destination MAC address triggers point-to-point unicast forwarding instead of unknown unicast flooding.

Anahtar Kavram

Layer 2 frame processing pipeline: MAC learning occurs on ingress before destination lookup and forwarding.
Soru 5Soru →

A Cisco Catalyst switch operating with default MAC address table aging timer settings (300 seconds) has an existing dynamic entry for Host A (MAC: 0010.a412.1111) on interface GigabitEthernet0/1 with a current age of 295 seconds. At time t=0t = 0 seconds, Host B (MAC: 0010.a412.2222) connected to GigabitEthernet0/2 sends a unicast frame destined to Host A. Host A sends no traffic during this period. At time t=10t = 10 seconds, Host B sends a second unicast frame destined to Host A. How does the switch process the frame sent at t=10t = 10 seconds?

Cevabı ve açıklamayı göster

Cevap: The switch floods the frame out all operational ports within the VLAN except GigabitEthernet0/2 because Host A's entry aged out 5 seconds prior.

Cevap

The switch floods the frame out all operational ports within the VLAN except GigabitEthernet0/2 because Host A's entry aged out 5 seconds prior.
Switches update and refresh MAC address table entries strictly based on the Source MAC address of ingress frames. When Host B sends a frame destined for Host A at t = 0 seconds, Host A's entry timer is NOT reset because Host A did not transmit any frame. Consequently, Host A's dynamic entry reaches the 300-second threshold at t = 5 seconds and is removed from the MAC table. When Host B sends another frame at t = 10 seconds, the switch finds no matching destination entry and floods the unknown unicast frame out all active ports in the VLAN except the receiving port (GigabitEthernet0/2).

Adım Adım Çözüm

1
Analyze MAC address table aging mechanics for the frame transmitted at t = 0 seconds.
Host B (0010.a412.2222) is learned on GigabitEthernet0/2. The frame is forwarded out GigabitEthernet0/1 using Host A's existing MAC table entry.
MAC address aging timers are refreshed ONLY when a frame is received containing that MAC address as the Source MAC. Destined (destination MAC) lookups do not reset the aging timer.
2
Calculate the expiration time of Host A's MAC address entry.
Host A's entry had an age of 295 seconds at t = 0. With a 300-second default timer and no incoming frames originating from Host A, the entry expires at t = 5 seconds (295 + 5 = 300 seconds).
Host A remained silent, so no frames with Source MAC 0010.a412.1111 entered the switch to reset the timer.
3
Evaluate the switch forwarding logic for the frame sent at t = 10 seconds.
At t = 10 seconds, the destination MAC 0010.a412.1111 is no longer in the MAC address table. The switch performs unknown unicast flooding.
When a destination unicast MAC address is not present in the L2 MAC table, Layer 2 switches flood the frame out all active interfaces in the same VLAN except the ingress port.

Anahtar Kavram

L2 MAC Table Aging and Unknown Unicast Flooding Logic
Soru 6Soru →

A Cisco Catalyst switch maintains the following dynamic MAC address table entries across multiple VLANs:

VLANMAC AddressTypePort
100050.56a1.1a01DYNAMICGigabitEthernet0/1
100050.56a2.2b02DYNAMICGigabitEthernet0/2
200050.56a1.1a01DYNAMICGigabitEthernet0/3

A host connected to port GigabitEthernet0/1 sends an ingress Ethernet frame tagged for VLAN 20 with a Source MAC address of 0050.56a1.1a010050.56a1.1a01 and a Destination MAC address of 0050.56a3.3c030050.56a3.3c03.

How does the switch update its MAC address table and handle the forwarding of this ingress frame?

Cevabı ve açıklamayı göster

Cevap: The switch updates the VLAN 20 MAC address table entry for 0050.56a1.1a01 to port GigabitEthernet0/1 while preserving the VLAN 10 entry, and floods the frame out all active VLAN 20 ports except GigabitEthernet0/1.

Cevap

The switch updates the VLAN 20 MAC table entry for source MAC 0050.56a1.1a01 to GigabitEthernet0/1 while preserving the VLAN 10 entry, and floods the unknown unicast frame out all active interfaces belonging to VLAN 20 except the ingress port GigabitEthernet0/1.
The correct response reflects two core switching mechanics: (1) Per-VLAN MAC learning updates the MAC address table for VLAN 20 on port GigabitEthernet0/1 without impacting entries in other VLANs (such as VLAN 10). (2) Destination MAC address lookup for an unlisted MAC address causes the switch to treat the frame as unknown unicast, flooding it out all active ports in VLAN 20 except the port on which the frame was received.

Adım Adım Çözüm

1
Examine the ingress frame's VLAN tag, Source MAC address, and ingress interface.
The ingress frame is tagged for VLAN 20, has Source MAC 0050.56a1.1a01, and arrives on port GigabitEthernet0/1.
Source MAC learning occurs on every incoming frame within the context of the frame's assigned VLAN.
2
Perform MAC address learning/station move update for VLAN 20.
The MAC table entry for VLAN 20 and MAC 0050.56a1.1a01 is updated from GigabitEthernet0/3 to GigabitEthernet0/1. The VLAN 10 table entry remains intact.
Cisco Catalyst switches maintain independent per-VLAN MAC address tables (PVST / per-VLAN learning context). Updating an entry in VLAN 20 does not purge entries in VLAN 10.
3
Perform Destination MAC lookup for 0050.56a3.3c03 in VLAN 20.
Destination MAC 0050.56a3.3c03 is not found in the VLAN 20 MAC address table (Unknown Unicast).
Layer 2 switches check the destination MAC address against the forwarding table for the matching VLAN.
4
Determine the Layer 2 forwarding decision for an unknown unicast frame.
The switch floods the frame out all operational access/trunk interfaces forwarding for VLAN 20, excluding the ingress port GigabitEthernet0/1.
Unknown unicast traffic must be flooded within the broadast domain (VLAN boundary) to reach the intended destination, but ingress interface split-horizon rules prevent returning the frame out its receiving port.

Anahtar Kavram

Per-VLAN MAC Address Table Operation and Unknown Unicast Flooding
Soru 7Soru →

A Cisco Catalyst switch receives an Ethernet frame on interface GigabitEthernet0/12 configured as an access port in VLAN 30. The incoming frame has a source MAC address of 00e0.8b11.2233 and a destination MAC address of 00e0.8b99.8877. The switch's MAC address table currently contains no entries for interface GigabitEthernet0/12 and does not contain the destination MAC address. Which two actions does the switch perform upon receiving this frame? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: The switch records the source MAC address 00e0.8b11.2233 associated with interface GigabitEthernet0/12 in its VLAN 30 MAC address table.; The switch floods the frame out all operational ports assigned to VLAN 30, excluding the receiving interface GigabitEthernet0/12.

Cevap

The switch records the source MAC address 00e0.8b11.2233 associated with interface GigabitEthernet0/12 in its VLAN 30 MAC address table, and floods the frame out all operational ports assigned to VLAN 30, excluding the receiving interface GigabitEthernet0/12.
When a switch receives a frame, it performs two distinct steps: MAC learning based on the source MAC address, and frame forwarding based on the destination MAC address. First, it records the source MAC address 00e0.8b11.2233 and its associated ingress port GigabitEthernet0/12 in the MAC table for VLAN 30. Second, because the destination MAC address 00e0.8b99.8877 is not in the MAC table, the switch handles it as unknown unicast traffic by flooding it to all other active ports configured in VLAN 30, excluding ingress port GigabitEthernet0/12.

Adım Adım Çözüm

1
Examine source MAC address processing.
The switch reads source MAC 00e0.8b11.2233 on ingress interface GigabitEthernet0/12 (VLAN 30) and updates its MAC address table entry for VLAN 30.
MAC address table learning is performed based on the source MAC address of incoming frames.
2
Examine destination MAC address lookup.
Because destination MAC 00e0.8b99.8877 is not in the MAC address table for VLAN 30, the frame is classified as unknown unicast.
Unknown unicast frames must be flooded within the VLAN scope.
3
Determine forwarding interface scope.
The frame is forwarded to all active ports in VLAN 30 except ingress port GigabitEthernet0/12.
Flooding rules dictate forwarding to all ports in the same broadcast domain except the receiving port.

Anahtar Kavram

L2 Switching MAC Address Table Learning and Unknown Unicast Flooding
Soru 8Soru →

A Cisco Catalyst switch with an initially empty MAC address table receives an Ethernet frame on ingress port FastEthernet0/1. The frame originates from Host A (MAC address 00A1.1111.AAAA) and is addressed to Host B (MAC address 00B2.2222.BBBB) on VLAN 10. In what chronological sequence does the Layer 2 switch execute internal processing steps from frame ingress to frame egress?

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct chronological sequence is: 1) Parse ingress frame for MAC addresses, 2) Learn source MAC and map to ingress port, 3) Lookup destination MAC in table, 4) Identify destination as unknown unicast, 5) Flood frame out all VLAN ports except ingress port.
When a Layer 2 switch receives an Ethernet frame on an ingress interface, it processes the frame in a specific order: first, it parses the L2 header; second, it reads the source MAC address and updates/populates its MAC address table (CAM table); third, it looks up the destination MAC address; fourth, if the destination is missing from the CAM table, it classifies it as an unknown unicast; fifth, it floods the frame out all active ports assigned to that VLAN except the receiving port.

Adım Adım Çözüm

1
Receive and ingress-parse frame
Identified Source MAC: 00A1.1111.AAAA, Destination MAC: 00B2.2222.BBBB, Ingress Port: Fa0/1, VLAN: 10.
The switch ASIC must inspect the Layer 2 Ethernet header preamble and fields first.
2
Source MAC Learning
MAC table entry updated with [VLAN 10 | 00A1.1111.AAAA | Dynamic | Fa0/1].
Layer 2 switches always learn source MAC addresses before determining egress forwarding.
3
Destination MAC Lookup
Query for 00B2.2222.BBBB yields no matching entry in VLAN 10 CAM table.
Switch determines whether to perform known unicast forwarding or unknown unicast flooding.
4
Classification of Traffic
Traffic categorized as unknown unicast.
A table miss forces the switch to default to broadcast-like flooding behavior within Layer 2 bounds.
5
Egress Frame Flooding
Frame replicated to all operational VLAN 10 ports, suppressing Fa0/1.
Split-horizon rule prevents sending a frame back out the interface from which it was received.

Anahtar Kavram

Layer 2 MAC Address Table Operation and Ingress/Egress Forwarding Pipeline
Soru 9Soru →

A Cisco Catalyst switch receives an ingress Ethernet frame tagged for VLAN 10 on port GigabitEthernet0/1. The frame contains a source MAC address of 0010.AB12.3456 and a destination MAC address of 0020.CD34.5678. Prior to receiving this frame, the switch MAC address table contains a dynamic entry listing 0010.AB12.3456 on port GigabitEthernet0/2 in VLAN 10, and a static entry listing 0020.CD34.5678 on port GigabitEthernet0/3 in VLAN 10. Port GigabitEthernet0/4 is an active access port configured in VLAN 20, while port GigabitEthernet0/5 is an active 802.1Q trunk port allowing VLANs 10 and 20. Which two actions does the switch perform upon processing this frame?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: It updates the MAC address table entry for 0010.AB12.3456 to associate it with port GigabitEthernet0/1 in VLAN 10.; It forwards the frame exclusively out port GigabitEthernet0/3.

Cevap

The switch updates its MAC address table entry for source MAC 0010.AB12.3456 to port GigabitEthernet0/1 in VLAN 10, and forwards the frame directly out port GigabitEthernet0/3.
When an Ethernet switch receives a frame, it performs learning and forwarding independently. First, it reads the source MAC address 0010.AB12.3456 and updates the MAC address table entry to map to port GigabitEthernet0/1 in VLAN 10. Second, it looks up the destination MAC address 0020.CD34.5678 in the MAC table for VLAN 10. Because a matching entry exists for GigabitEthernet0/3, the switch forwards the frame directly out GigabitEthernet0/3 without flooding.

Adım Adım Çözüm

1
Analyze ingress port processing and source MAC learning logic.
The source MAC address 0010.AB12.3456 arrived on GigabitEthernet0/1 in VLAN 10. The switch updates the existing table mapping for 0010.AB12.3456 from GigabitEthernet0/2 to GigabitEthernet0/1.
Layer 2 switches evaluate every incoming frame's source MAC address to build and maintain up-to-date MAC table port mappings.
2
Analyze egress port forwarding logic based on destination MAC lookup.
The destination MAC 0020.CD34.5678 is matched in the MAC table for VLAN 10 pointing to GigabitEthernet0/3.
When a match is found in the MAC table for the frame's destination address in the matching VLAN, known unicast forwarding directs the frame solely to that designated egress interface.

Anahtar Kavram

Layer 2 MAC address table dynamic learning, station movement handling, and known unicast forwarding logic.
Soru 10Soru →

A Cisco Catalyst switch contains the following entry in its MAC address table for VLAN 10:

VLANMAC AddressTypePort
10000a.1111.2222DynamicGigabitEthernet0/1
10000b.3333.4444DynamicGigabitEthernet0/2

A network technician disconnects the host with MAC address 000a.1111.2222 from port GigabitEthernet0/1 and reconnects it to port GigabitEthernet0/3. The host immediately transmits an Ethernet frame destined for MAC address 000b.3333.4444 into port GigabitEthernet0/3 on VLAN 10. How will the switch handle MAC address learning and frame forwarding for this ingress traffic?

Cevabı ve açıklamayı göster

Cevap: It updates the MAC address table entry for 000a.1111.2222 to associate with GigabitEthernet0/3 and forwards the frame exclusively out GigabitEthernet0/2.

Cevap

The switch updates the MAC address table entry for 000a.1111.2222 to point to GigabitEthernet0/3 and forwards the frame directly out GigabitEthernet0/2.
When an Ethernet frame arrives on port GigabitEthernet0/3, the switch reads the source MAC address 000a.1111.2222. Recognizing that this address was previously assigned to GigabitEthernet0/1, it performs a station move update by rewriting the MAC table entry to GigabitEthernet0/3. Next, the switch looks up the destination MAC address 000b.3333.4444. Since an entry already exists pointing to GigabitEthernet0/2, the switch forwards the frame as a known unicast transmission exclusively out GigabitEthernet0/2.

Adım Adım Çözüm

1
Inspect the ingress frame's source MAC address and ingress port.
Source MAC 000a.1111.2222 is received on GigabitEthernet0/3.
Layer 2 switches perform MAC learning by examining the source MAC address of every incoming frame.
2
Update the MAC address table for station movement.
The dynamic entry for 000a.1111.2222 is updated from GigabitEthernet0/1 to GigabitEthernet0/3.
When a source MAC address is seen on a new interface, the switch updates the existing table mapping immediately.
3
Lookup the destination MAC address 000b.3333.4444 in the MAC address table.
Destination MAC 000b.3333.4444 is matched to egress port GigabitEthernet0/2.
Known unicast destination addresses result in point-to-point forwarding to the registered port.
4
Forward the Ethernet frame.
The frame is forwarded solely out GigabitEthernet0/2.
Because the destination port is known and distinct from the ingress port, no flooding or dropping occurs.

Anahtar Kavram

L2 Switching Station Movement and Known Unicast Forwarding
Soru 11Soru →

A Cisco Catalyst switch receives an Ethernet frame on ingress port GigabitEthernet0/1 with Source MAC address 0010.ab12.3456 and Destination MAC address 0020.cd78.90ab. The switch's current MAC address table records 0010.ab12.3456 as learned on GigabitEthernet0/3, but has no entry for 0020.cd78.90ab. Which TWO actions will the switch perform upon processing this ingress frame? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: Update the MAC address table entry for 0010.ab12.3456 to associate it with port GigabitEthernet0/1.; Flood the frame out all operational ports within the same VLAN, excluding ingress port GigabitEthernet0/1.

Cevap

The switch updates the MAC address table entry for 0010.ab12.3456 to GigabitEthernet0/1 and floods the unknown unicast frame out all operational ports on the VLAN except GigabitEthernet0/1.
When an Ethernet frame arrives at a switch port, the switch first performs MAC address learning by checking the frame's source MAC address. If the source MAC address exists in the MAC table but is associated with a different interface, the switch updates the table entry with the new ingress port (station move update). Next, the switch looks up the frame's destination MAC address. Because the destination MAC address is not present in the MAC table, the switch treats the frame as unknown unicast and floods it out all active ports in the same VLAN except the receiving port.

Adım Adım Çözüm

1
Examine the source MAC address handling (MAC Learning & Station Move).
The source MAC address 0010.ab12.3456 was previously listed on GigabitEthernet0/3. Since it arrived on GigabitEthernet0/1, the switch rewrites the table entry to associate 0010.ab12.3456 with GigabitEthernet0/1.
Layer 2 switches dynamically update dynamic MAC table entries whenever a known MAC address arrives on a different port.
2
Examine the destination MAC address handling (Forwarding Decision).
The destination MAC address 0020.cd78.90ab is missing from the MAC address table.
When a destination MAC address is not found in the Layer 2 forwarding table, the frame is classified as an unknown unicast frame.
3
Execute unknown unicast forwarding logic.
The frame is flooded to all active ports assigned to the same VLAN, except the receiving interface (GigabitEthernet0/1).
Unknown unicast traffic must be flooded across the broadcast domain so the intended destination host can receive it and respond.

Anahtar Kavram

Layer 2 MAC Table Station Learning and Unknown Unicast Flooding Mechanics
Soru 12Soru →

A switch receives an Ethernet frame on port FastEthernet0/1. The source MAC address is 0000.1111.1111, and the unicast destination MAC address is 0000.2222.2222. The switch checks its MAC address table and finds no entry for 0000.2222.2222. What action does the switch take to handle this frame?

Cevabı ve açıklamayı göster

Cevap: Floods the frame out all operational interfaces except the ingress port FastEthernet0/1.

Cevap

The switch floods the frame out all operational interfaces within the VLAN except the ingress port FastEthernet0/1.
When a Layer 2 switch receives a unicast frame whose destination MAC address is not currently in its MAC address table, it performs unknown unicast flooding. This forwards the frame out every active port belonging to the same VLAN, excluding the port on which the frame was received.

Adım Adım Çözüm

1
Examine the source MAC address processing.
The switch records MAC address 0000.1111.1111 in its MAC address table mapped to port FastEthernet0/1 if it is not already present.
Switches learn MAC addresses dynamically from incoming frames' source MAC addresses.
2
Examine the destination MAC address lookup.
The destination MAC address 0000.2222.2222 is determined to be an unknown unicast address because it is not present in the MAC address table.
Forwarding decisions are made based on looking up the destination MAC address in the switch MAC address table.
3
Determine the forwarding behavior for unknown unicast traffic.
The switch floods the frame out all active switch ports in the VLAN, except for the incoming port FastEthernet0/1.
Flooding unknown unicast traffic ensures the destination host receives the packet regardless of which port it is connected to.

Anahtar Kavram

Unknown Unicast Flooding and MAC Address Table Lookup Operations
Soru 13Soru →

When a Layer 2 Ethernet switch receives an ingress frame, it processes the header information in a specific sequential order. Place the steps taken by the switch into the correct chronological order from first to last.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct order of switch operation is: 1) The frame arrives on an ingress port, 2) The switch learns or updates the source MAC address and port mapping in the MAC address table, 3) The switch performs a table lookup for the destination MAC address, and 4) The switch forwards or floods the frame out the appropriate port(s).
A Layer 2 Ethernet switch always follows a standard pipeline: frame reception on ingress, source MAC learning and table updating, destination MAC address lookup, and finally executing unicast forwarding or VLAN flooding.

Adım Adım Çözüm

1
Receive ingress frame
The physical frame is received on an active Layer 2 switch port.
Initial reception triggers Layer 2 inspection.
2
Source MAC learning
The source MAC address is mapped to the ingress port in the MAC address table.
Switches always learn source MAC locations before executing forwarding logic.
3
Destination MAC lookup
The MAC address table is searched for the destination MAC address.
Determines whether the egress interface is known or unknown.
4
Frame forwarding decision
The frame is unicast forwarded to a single port or flooded across the VLAN (excluding ingress port).
Completes the Layer 2 delivery cycle.

Anahtar Kavram

Layer 2 Frame Ingress Processing and MAC Table Pipeline
Soru 14Soru →

Switch SW1 receives a unicast frame on ingress port GigabitEthernet0/2. The frame contains a source MAC address of 7069.5a12.1234 and a destination MAC address of 0011.2233.4455. The MAC address table of SW1 currently has no entries. Which two actions does the switch perform upon receiving this frame? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: The switch records the source MAC address 7069.5a12.1234 and ingress port GigabitEthernet0/2 in its MAC address table.; The switch floods the frame out all active ports assigned to the same VLAN, excluding port GigabitEthernet0/2.

Cevap

The switch records the source MAC address on ingress port GigabitEthernet0/2 in its MAC address table and floods the frame out all operational ports in the same VLAN except GigabitEthernet0/2.
When an Ethernet switch receives a frame, it executes two key processes: learning and forwarding. First, it reads the source MAC address (7069.5a12.1234) and maps it to the receiving interface (GigabitEthernet0/2) in its MAC address table. Second, because the destination MAC address (0011.2233.4455) is not listed in its table, the frame is treated as an unknown unicast frame. The switch floods the frame out every operational port in the VLAN except the ingress port where the frame was received.

Adım Adım Çözüm

1
Examine the ingress frame's source MAC address and ingress interface.
The switch adds an entry for source MAC 7069.5a12.1234 mapped to port GigabitEthernet0/2.
Layer 2 switches perform dynamic MAC learning by recording the source address of every incoming frame.
2
Examine the ingress frame's destination MAC address against the MAC address table.
Destination MAC 0011.2233.4455 is not found in the table, identifying the frame as an unknown unicast frame.
An empty MAC table contains no matching entry for the destination.
3
Apply Layer 2 forwarding rules for an unknown unicast frame.
The frame is flooded out all active ports in the same VLAN except ingress port GigabitEthernet0/2.
Flooding ensures the unknown destination host receives the frame without retransmitting traffic out the ingress port.

Anahtar Kavram

L2 Switching Concepts and MAC Table Operation
Tahmini Süre:1m 0s
Soru 15Soru →

A Cisco Catalyst switch receives an Ethernet frame on access port GigabitEthernet0/1 configured in VLAN 10. The frame contains a source MAC address of 0011.2233.4455 and a unicast destination MAC address of 00aa.bbcc.dde1. The switch currently maintains the following dynamic MAC address table entries:

VLANMAC AddressTypePort
100011.2233.4455DYNAMICGigabitEthernet0/2
1000aa.bbcc.dde1DYNAMICGigabitEthernet0/3
2000aa.bbcc.dde1DYNAMICGigabitEthernet0/4

Which set of actions will the switch take upon processing this ingress frame?

Cevabı ve açıklamayı göster

Cevap: Update the VLAN 10 entry for 0011.2233.4455 to GigabitEthernet0/1 and forward the frame out GigabitEthernet0/3 only.

Cevap

Update the VLAN 10 entry for 0011.2233.4455 to GigabitEthernet0/1 and forward the frame out GigabitEthernet0/3 only.
When an Ethernet frame enters a switch port, the switch inspects the source MAC address to maintain its MAC address table. Since MAC 0011.2233.4455 was previously recorded on GigabitEthernet0/2 but arrived on GigabitEthernet0/1 in VLAN 10, the switch updates the table entry to point to GigabitEthernet0/1. Next, the switch inspects the destination MAC address 00aa.bbcc.dde1 within VLAN 10. Finding a matching dynamic entry for GigabitEthernet0/3 in VLAN 10, the switch forwards the frame exclusively out GigabitEthernet0/3.

Adım Adım Çözüm

1
Examine the source MAC address and ingress port/VLAN context.
The source MAC address 0011.2233.4455 arrives on GigabitEthernet0/1 in VLAN 10. The current MAC table lists this address on GigabitEthernet0/2 for VLAN 10.
When a host moves or changes ports, receiving a frame on a new port triggers the switch to update (re-learn) the MAC address table entry for that specific VLAN.
2
Perform a destination MAC address lookup within the ingress VLAN.
The destination MAC address 00aa.bbcc.dde1 is present in the MAC table under VLAN 10 associated with port GigabitEthernet0/3.
Switches isolate forwarding decisions per VLAN. The matching entry in VLAN 20 on GigabitEthernet0/4 is ignored.
3
Determine the forwarding action.
The switch performs known unicast forwarding by transmitting the frame out GigabitEthernet0/3 only.
Since the destination MAC address is known within VLAN 10, no unknown unicast flooding is required.

Anahtar Kavram

Layer 2 MAC Table Learning, Station Mobility, and Per-VLAN Forwarding Decisions
Tahmini Süre:2m 0s
Soru 16Soru →

Host A with MAC address 0011.2233.4455 is connected to interface FastEthernet0/5 assigned to VLAN 20 on switch SW-Central. The MAC address table on SW-Central contains no existing entries for VLAN 20. When Host A transmits an ARP request frame to resolve its default gateway IP address, which operational sequence will SW-Central perform upon receiving the ingress frame?

Cevabı ve açıklamayı göster

Cevap: Learn source MAC 0011.2233.4455 on interface FastEthernet0/5 in VLAN 20, then flood the frame out all active interfaces assigned to VLAN 20 except FastEthernet0/5.

Cevap

The switch records MAC 0011.2233.4455 on interface FastEthernet0/5 in VLAN 20 and floods the frame out all active interfaces in VLAN 20 except FastEthernet0/5.
When a Layer 2 switch receives an Ethernet frame, it first updates its MAC address table by associating the source MAC address (0011.2233.4455) with the receiving port (FastEthernet0/5) and VLAN (VLAN 20). Next, because an ARP request uses the Ethernet broadcast destination address (FFFF.FFFF.FFFF), the switch floods the frame out every port in VLAN 20 except the ingress interface.

Adım Adım Çözüm

1
Examine the source MAC address of the incoming Ethernet frame.
The source MAC address 0011.2233.4455 is identified on port FastEthernet0/5.
Layer 2 switches perform dynamic MAC address learning by inspecting the source MAC field of all ingress frames.
2
Update the switch MAC address table for VLAN 20.
An entry mapping MAC 0011.2233.4455 to port FastEthernet0/5 in VLAN 20 is created.
MAC table entries are stored per-VLAN to maintain Layer 2 traffic isolation.
3
Examine the destination MAC address of the frame.
The destination MAC address is FFFF.FFFF.FFFF (Ethernet broadcast).
ARP requests use the broadcast destination MAC address so that all devices in the broadcast domain receive the query.
4
Forward the broadcast frame according to Layer 2 switching rules.
The frame is flooded to all active ports belonging to VLAN 20, excluding ingress port FastEthernet0/5.
Broadcast frames must reach all hosts in the same VLAN domain, but split-horizon logic prevents sending the frame back out its ingress port.

Anahtar Kavram

L2 Switch MAC Table Operation and Broadcast Flooding Rules
Tahmini Süre:1m 15s
Soru 17Soru →

A Cisco Catalyst switch receives an ingress Ethernet frame on interface GigabitEthernet0/1 assigned to VLAN 10. The frame contains a source MAC address that does not currently exist in the MAC address table and a destination MAC address that is already registered on interface GigabitEthernet0/2 in VLAN 10. Arrange the switch processing actions in the correct chronological sequence from initial frame reception to egress forwarding.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence is: (1) Frame reception and header parsing on GigabitEthernet0/1, (2) Learning the source MAC address by adding an entry for GigabitEthernet0/1 in VLAN 10, (3) Looking up the destination MAC address in the MAC address table, and (4) Forwarding the unicast frame out GigabitEthernet0/2.
When a switch receives a frame, it follows a strict sequence of operations: first receiving and parsing the header, then learning the source MAC address (adding/updating the MAC table entry for the ingress port), looking up the destination MAC address in the table, and finally forwarding the frame out the designated destination interface.

Adım Adım Çözüm

1
Analyze frame ingress
The switch receives the frame on interface GigabitEthernet0/1, identifying VLAN 10, source MAC, and destination MAC.
Header parsing is the initial hardware step when a frame enters a switchport.
2
Process source MAC learning
The switch adds a dynamic entry mapping the unknown source MAC address to GigabitEthernet0/1 in VLAN 10.
Cisco switches perform Layer 2 source MAC learning before evaluating destination forwarding.
3
Perform destination lookup
The MAC address table search matches the destination MAC to interface GigabitEthernet0/2.
Destination address matching dictates whether a frame is forwarded to a single port or flooded.
4
Execute frame forwarding
The frame is forwarded directly out GigabitEthernet0/2.
Known unicast frames are forwarded solely out the egress port specified in the MAC table.

Anahtar Kavram

Layer 2 Switch Ingress Processing & MAC Address Table Operation
Soru 18Soru →

An enterprise Catalyst switch has recently rebooted, and its MAC address table is entirely empty. Host Workstation-1 is connected to port FastEthernet0/12 in VLAN 10 and sends a unicast frame addressed to Server-1 (MAC address 0050.56a1.1a02). The frame enters FastEthernet0/12 carrying a source MAC address of 0050.56a1.1a01. How will the switch process this incoming Ethernet frame?

Cevabı ve açıklamayı göster

Cevap: The switch records MAC address 0050.56a1.1a01 mapped to port FastEthernet0/12 in VLAN 10, and floods the frame out all operational ports assigned to VLAN 10 except FastEthernet0/12.

Cevap

The switch records MAC address 0050.56a1.1a01 mapped to port FastEthernet0/12 in VLAN 10, and floods the frame out all operational ports assigned to VLAN 10 except FastEthernet0/12.
When a Layer 2 switch receives an Ethernet frame, it first inspects the source MAC address and associates it with the ingress port and VLAN in its MAC address table. Next, it looks up the destination MAC address. Because the MAC table is empty, the destination MAC is unknown. The switch performs unknown unicast flooding by forwarding the frame out every active port assigned to the same VLAN, excluding the port on which the frame arrived.

Adım Adım Çözüm

1
Examine the ingress frame's source MAC address and ingress port.
The source MAC address is 0050.56a1.1a01 on ingress port FastEthernet0/12 (VLAN 10).
Layer 2 switches dynamically build their MAC address table by inspecting the source MAC address of every incoming Ethernet frame.
2
Update the MAC address table entry for VLAN 10.
An entry mapping 0050.56a1.1a01 to FastEthernet0/12 in VLAN 10 is added or refreshed.
Learning source MAC addresses ensures future frames destined for Workstation-1 can be forwarded directly via unicast.
3
Lookup the destination MAC address 0050.56a1.1a02 in the MAC address table.
The destination MAC address is not found (unknown unicast).
The switch MAC address table was cleared after reboot and has not yet observed traffic originating from Server-1.
4
Determine the forwarding action for the unknown unicast frame.
The frame is flooded out all active switch ports belonging to VLAN 10, except the ingress port FastEthernet0/12.
Flooding guarantees delivery to the destination host while restricting traffic within the VLAN boundary and preventing hairpinning back out the ingress port.

Anahtar Kavram

L2 Switching Concepts and MAC Table Operation
Soru 19Soru →

An engineer is troubleshooting traffic flow on switch SW-BuildingA. A connected device sends an Ethernet frame that arrives on interface GigabitEthernet0/4. The frame has a source MAC address of 0050.56a1.1a2b and a destination MAC address of 0050.56b2.2c3d. When the switch performs a lookup for the destination MAC address in its MAC address table, it identifies an existing dynamic entry mapping 0050.56b2.2c3d to GigabitEthernet0/4. Which action will the switch perform for this frame?

Cevabı ve açıklamayı göster

Cevap: Learns or updates the source MAC address entry on GigabitEthernet0/4 and filters (drops) the frame.

Cevap

The switch updates or records the source MAC address entry on the ingress port (GigabitEthernet0/4) and filters (drops) the frame without forwarding it.
When a Layer 2 switch receives a frame, it reads the source MAC address to update its MAC address table. Next, it looks up the destination MAC address. If the destination MAC address maps to the exact same port on which the frame arrived, the switch filters (drops) the frame because the destination node is already on that local segment and does not need switch forwarding.

Adım Adım Çözüm

1
Examine the ingress interface and source MAC address of the incoming Ethernet frame.
The switch records or updates the MAC address 0050.56a1.1a2b associated with interface GigabitEthernet0/4 in the MAC address table.
Layer 2 switches constantly learn and refresh source MAC address table bindings upon receiving incoming frames.
2
Perform a destination MAC address table lookup for 0050.56b2.2c3d.
The lookup matches an existing dynamic entry pointing to interface GigabitEthernet0/4.
The switch needs to determine which egress port corresponds to the destination host.
3
Compare the egress interface identified in the MAC table lookup with the ingress interface of the frame.
The egress interface (GigabitEthernet0/4) matches the ingress interface (GigabitEthernet0/4).
When ingress and egress ports match, the frame is already present on that physical network segment.
4
Apply frame forwarding/filtering rules based on matching ports.
The switch filters (drops) the frame.
Forwarding the frame back out the ingress port is unnecessary and would cause duplicate frames on a shared Layer 2 segment.

Anahtar Kavram

Frame Filtering and MAC Address Table Lookup Rules
Soru 20Soru →

A Cisco Catalyst switch receives an Ethernet frame on interface GigabitEthernet0/3 configured in VLAN 15. The frame contains a source MAC address of 0050.56a1.1a01 and a destination MAC address of 0050.56a1.2b02. Upon reviewing its MAC address table, the switch finds that destination 0050.56a1.2b02 is already dynamic mapping to interface GigabitEthernet0/3 in VLAN 15, but there is no entry for source MAC address 0050.56a1.1a01. Which action will the switch perform upon receiving this frame?

Cevabı ve açıklamayı göster

Cevap: The switch records the source MAC address 0050.56a1.1a01 on interface GigabitEthernet0/3 in VLAN 15 and filters (drops) the frame.

Cevap

The switch records the source MAC address 0050.56a1.1a01 on interface GigabitEthernet0/3 in VLAN 15 and filters (drops) the frame.
When an Ethernet frame reaches a switch port, the switch always performs MAC address learning first by inspecting the frame's source MAC address and updating its MAC address table with the ingress port and VLAN. Next, the switch looks up the destination MAC address to make a forwarding decision. If the destination MAC address is located on the exact same port where the frame entered, the switch determines that the destination host is already on the local collision domain/segment and filters (drops) the frame to avoid sending redundant traffic.

Adım Adım Çözüm

1
Examine ingress frame header and process source MAC address learning
The switch inspects the source MAC address (0050.56a1.1a01) and adds an entry mapping 0050.56a1.1a01 to interface GigabitEthernet0/3 in VLAN 15 in its MAC address table.
Layer 2 switches learn source MAC addresses from all incoming Ethernet frames on the port they arrive on.
2
Lookup destination MAC address in the MAC address table
The destination MAC address (0050.56a1.2b02) is found in the MAC address table and is mapped to interface GigabitEthernet0/3 in VLAN 15.
Switch lookup determines which egress port should be used to reach the target destination.
3
Compare ingress port with target egress port and apply forwarding/filtering logic
Since the target egress port (GigabitEthernet0/3) matches the ingress port (GigabitEthernet0/3), the frame is filtered (dropped).
Devices connected through a hub or shared segment on GigabitEthernet0/3 receive local traffic directly; retransmitting the frame out the same port would create unnecessary collision and traffic overhead.

Anahtar Kavram

Layer 2 Frame Filtering and MAC Address Table Operation
Sayfa 1 / 2Sonraki