An administrator connects two Cisco switches, Switch-1 and Switch-2, using interface GigabitEthernet0/1. Switch-1 is configured with `switchport mode dynamic desirable`, `switchport trunk native vlan 20`, and `switchport trunk allowed vlan 10,20,30`. Switch-2 is configured with `switchport mode dynamic auto`, `switchport trunk native vlan 20`, and `switchport trunk allowed vlan 10,30`. Which statement correctly describes the operational status and traffic behavior across this interswitch link?
- An 802.1Q trunk link forms successfully via DTP negotiation, but Switch-2 drops all ingress traffic for VLAN 20 because VLAN 20 is not included in its allowed VLAN list.Cevap
- BDTP negotiation fails to form a trunk link because the allowed VLAN lists on Switch-1 and Switch-2 do not match.
- CSwitch-2 accepts untagged frames from Switch-1 on the native VLAN and automatically tags them with VLAN 20 to bypass its allowed VLAN list filter.
- DBecause VLAN 20 is pruned on Switch-2, untagged VLAN 20 frames received by Switch-2 are automatically remapped to default VLAN 1.
Cevap
An 802.1Q trunk link forms successfully via DTP negotiation, but Switch-2 drops all ingress traffic for VLAN 20 because VLAN 20 is not included in its allowed VLAN list.
DTP successfully negotiates trunking between dynamic desirable and dynamic auto operational modes. However, trunk interface allowed VLAN lists filter traffic independently on each switch. Because Switch-2 has configured `switchport trunk allowed vlan 10,30`, VLAN 20 is explicitly pruned from Switch-2's trunk interface. Untagged traffic for native VLAN 20 arriving on Switch-2 will be mapped to VLAN 20 and subsequently dropped because VLAN 20 is not permitted on the trunk.
Adım Adım Çözüm
Anahtar Kavram
802.1Q Trunking DTP Negotiation and Allowed VLAN Pruning Mechanics
Tahmini Süre:1m 30s