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Zorluk: ZorL2 Switching Concepts and MAC Table Operation

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?

  1. Update the VLAN 10 entry for 0011.2233.4455 to GigabitEthernet0/1 and forward the frame out GigabitEthernet0/3 only.Cevap
  2. B
    Update the VLAN 10 entry for 0011.2233.4455 to GigabitEthernet0/1 and flood the frame out all active ports in VLAN 10 except GigabitEthernet0/1.
  3. C
    Forward the frame out GigabitEthernet0/4 because it has a higher-numbered port matching destination 00aa.bbcc.dde1 without updating the MAC table.
  4. D
    Drop the frame immediately because source MAC address 0011.2233.4455 is already bound to GigabitEthernet0/2 in the MAC table.

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
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Konular

L2 Switching Concepts and MAC Table Operation

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