A network administrator is troubleshooting an 802.1Q trunk link between Switch-A and Switch-B. Host computers on VLAN 20 attached to Switch-B are unable to communicate with the default gateway located on Switch-A. Inspection of the trunk configuration reveals two issues: Switch-A is configured with native VLAN 20 while Switch-B is configured with native VLAN 1, and VLAN 20 is currently missing from the allowed VLAN list on Switch-B's trunk interface. Which TWO of the following statements accurately explain the technical causes of the communication failure in this setup? (Select TWO.)
- Untagged frames transmitted from VLAN 20 on Switch-A will be associated with VLAN 1 when received by Switch-B.Cevap
- Tagged frames for VLAN 20 sent from Switch-A will be dropped by Switch-B's trunk interface.Cevap
- CHosts on VLAN 20 cannot reach the gateway because 802.1Q trunking disables Layer 2 forwarding when devices reside in different physical switches.
- DThe connectivity failure occurs because setting the STP bridge priority to 65535 on Switch-A forces it to block all trunk ports for VLAN 20.
Cevap
The two correct technical causes are that untagged frames transmitted from VLAN 20 on Switch-A will be associated with VLAN 1 when received by Switch-B, and tagged frames for VLAN 20 sent from Switch-A will be dropped by Switch-B's trunk interface.
The issue stems from two distinct trunking misconfigurations. First, a native VLAN mismatch (VLAN 20 on Switch-A vs. VLAN 1 on Switch-B) causes untagged frames sent from VLAN 20 on Switch-A to be incorrectly assigned to VLAN 1 upon arrival at Switch-B. Second, because VLAN 20 is missing from Switch-B's allowed VLAN list on the trunk, any tagged VLAN 20 frames arriving at or traversing Switch-B are dropped.
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Anahtar Kavram
802.1Q Trunking Native VLAN Mismatch and Allowed List Filtering