What Happens When Native VLAN Is Not Specified on One Switch?
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Question
Cisco Catalyst switches CAT1 and CAT2 have a connection between them using ports FA0/13. An 802.1Q trunk is configured between the two switches. On
CAT1, VLAN 10 is chosen as native, but on CAT2 the native VLAN is not specified. What will happen in this scenario?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.C
When two switches are connected together, a trunk is typically created between them to carry traffic for multiple VLANs. The 802.1Q trunking protocol is used to tag Ethernet frames with a VLAN ID, allowing traffic from multiple VLANs to be carried over a single physical link.
In this scenario, CAT1 and CAT2 are connected together using an 802.1Q trunk on port FA0/13. On CAT1, VLAN 10 has been chosen as the native VLAN, which means that untagged frames sent from this switch will be treated as belonging to VLAN 10. However, on CAT2, the native VLAN has not been specified.
If the native VLAN is not specified on CAT2, it will default to VLAN 1. This means that untagged frames sent from CAT2 will be treated as belonging to VLAN 1. This creates a native VLAN mismatch, which could cause problems with the trunk.
The correct answer is C: A native VLAN mismatch error message will appear. When a native VLAN mismatch occurs on a trunk, the switches will generate a warning message to alert the network administrator. The message will typically include information about which ports are involved in the mismatch and what the native VLANs are set to.
Option A is incorrect because 802.1Q giants frames are not related to native VLAN mismatches. Giants frames are frames that exceed the maximum frame size allowed on the network, which is typically 1518 bytes. These frames can cause performance problems, but they are not related to VLAN configuration.
Option B is also incorrect. If VLAN 10 is set as the native VLAN on CAT1, then all untagged frames sent from that switch will be treated as belonging to VLAN 10, not VLAN 1. Similarly, if the native VLAN is not specified on CAT2, untagged frames from that switch will be treated as belonging to VLAN 1, not VLAN 10.
Option D is incorrect because if the native VLAN is not specified on CAT2, untagged frames from that switch will be treated as belonging to VLAN 1, not VLAN 10. Therefore, frames from VLAN 10 on CAT1 will still be untagged when they are received by CAT2, rather than being tagged with VLAN 10.
