A network administrator is establishing an 802.1Q trunk connection between two core switches, SW-CORE-A and SW-CORE-B. The interface on SW-CORE-A is configured with a native VLAN of 20, whereas the interface on SW-CORE-B is configured with the default native VLAN of 1. Both switch interfaces explicitly allow VLANs 10, 20, and 30 across the trunk link.
Which of the following operational outcomes will occur as a result of this configuration mismatch? (Select TWO.)
- Untagged frames originating from VLAN 20 on SW-CORE-A will be placed into VLAN 1 upon arrival at SW-CORE-B.Cevap
- Control protocols such as CDP or PVST+ will generate native VLAN mismatch error messages in the system log.Cevap
- CSW-CORE-A will automatically encapsulate VLAN 20 frames with an 802.1Q tag header to ensure proper VLAN identification.
- DTagged traffic belonging to VLAN 10 will be dropped by both switches until the native VLAN mismatch is resolved.
Cevap
Untagged frames originating from VLAN 20 on SW-CORE-A will be placed into VLAN 1 upon arrival at SW-CORE-B, and control protocols such as CDP or PVST+ will generate native VLAN mismatch error messages in the system log.
On an IEEE 802.1Q trunk, frames belonging to the designated native VLAN are transmitted without a 4-byte VLAN tag. When SW-CORE-A sends untagged frames for VLAN 20, SW-CORE-B receives them without a tag and assigns them to its own configured native VLAN (VLAN 1), causing unintended traffic leakage between VLAN 20 and VLAN 1. Additionally, switch discovery and spanning-tree protocols (such as CDP and PVST+) exchange control frames that detect this native VLAN mismatch, generating log warnings to alert network administrators.
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Anahtar Kavram
802.1Q Native VLAN Tagging and Mismatch Symptoms