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Zorluk: ZorVLAN Configuration and 802.1Q Trunking

A network engineer is analyzing an 802.1Q trunk connection established between `SW-Access-01` and `SW-Core-01` on interface `GigabitEthernet0/1`. Interface configurations are as follows:

SW-Access-01:
text
interface GigabitEthernet0/1
switchport mode trunk
switchport trunk native vlan 1
switchport trunk allowed vlan 10,20,30

SW-Core-01:
text
interface GigabitEthernet0/1
switchport mode trunk
switchport trunk native vlan 10
switchport trunk allowed vlan 10,20,30

Assuming both switches are active and exchanging data, which TWO of the following statements accurately describe how untagged and tagged frames are processed across this link? (Select TWO)

  1. Untagged frames transmitted from VLAN 1 on SW-Access-01 will be forwarded into VLAN 10 upon arriving at SW-Core-01.Cevap
  2. B
    Frames originating from VLAN 10 on SW-Access-01 will egress the trunk untagged and be dropped by SW-Core-01.
  3. VLAN 10 traffic sent from SW-Core-01 will egress untagged and be assigned to VLAN 1 when received by SW-Access-01.Cevap
  4. D
    SW-Core-01 will drop all incoming VLAN 10 frames transmitted by SW-Access-01 because a Layer 3 router is required to translate trunk tags.

Cevap

Untagged frames transmitted from VLAN 1 on SW-Access-01 will be forwarded into VLAN 10 upon arriving at SW-Core-01, and VLAN 10 traffic sent from SW-Core-01 will egress untagged and be assigned to VLAN 1 when received by SW-Access-01.
On an 802.1Q trunk link, frames belonging to the configured native VLAN are transmitted without an 802.1Q tag, while frames from all other allowed VLANs are tagged. When a native VLAN mismatch exists between two switches, untagged frames sent by one switch are received and placed into the receiving switch's configured native VLAN. Specifically, untagged frames from VLAN 1 on the access switch arrive at the core switch and are assigned to VLAN 10. Conversely, VLAN 10 frames originating on the core switch are sent untagged because VLAN 10 is native on that switch; upon arrival at the access switch, these untagged frames are placed into VLAN 1.

Adım Adım Çözüm

1
Analyze frame encapsulation on SW-Access-01 for VLAN 1 and VLAN 10
Native VLAN on SW-Access-01 is VLAN 1. Therefore, VLAN 1 traffic is sent untagged, while VLAN 10 traffic is encapsulated with an 802.1Q tag bearing VLAN ID 10.
802.1Q trunks strip tags for traffic belonging to the local native VLAN and add tags for all other allowed VLANs.
2
Analyze ingress frame processing on SW-Core-01
Native VLAN on SW-Core-01 is VLAN 10. Any untagged frame arriving at SW-Core-01 is implicitly assigned to VLAN 10. Tagged frames with VLAN ID 10 are placed directly into VLAN 10.
Switches assign incoming untagged frames to whichever native VLAN is configured on the receiving trunk port.
3
Analyze egress frame processing from SW-Core-01 towards SW-Access-01
VLAN 10 frames leaving SW-Core-01 are stripped of tags because VLAN 10 is native on SW-Core-01. SW-Access-01 receives untagged frames and places them into its native VLAN 1.
Native VLAN mismatch causes asymmetrical traffic leakage between the two configured native VLANs across opposing switch ports.

Anahtar Kavram

802.1Q Native VLAN Processing & Tagging Behavior
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Konular

VLAN Configuration and 802.1Q Trunking

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