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Zorluk: OrtaL2 Switching Concepts and MAC Table Operation

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.

  1. 1The switch receives the Ethernet frame on interface GigabitEthernet0/1 and parses the Layer 2 header for source MAC, destination MAC, and VLAN membership.
  2. 2The switch updates the VLAN 10 MAC address table by creating a dynamic entry that binds the unknown source MAC address to interface GigabitEthernet0/1.
  3. 3The switch performs a MAC address table lookup for the frame's destination MAC address within the scope of VLAN 10.
  4. 4The switch identifies the existing entry for GigabitEthernet0/2 and forwards the unicast frame out interface GigabitEthernet0/2.

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
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