What does Switchport trunk allowed VLAN do?
The switchport trunk allowed vlan command is used to specify the list of VLANs that are allowed on a trunk port. When a Layer 2 interface on a Cisco IOS device is configured to operate in trunk mode, the default setting is for the interface to carry all of the VLANs defined on the switch.
How do you remove a trunk from a Switchport?
To configure the allowed VLANs for the private trunk interface, use the switchport private-vlan trunk allowed vlan command. To remove the allowed VLANs, sue the no form of this command.
Which command is used to specify the list of VLANs that are allowed on a trunk port we assume that both VLANs 10 and 20 are allowed on the trunk?
Cisco IOS switchport trunk allowed vlan vlan
Use the Cisco IOS switchport trunk allowed vlan vlan-list command to specify the list of VLANs to be allowed on the trunk link. In Figure 3-19, VLANs 10, 20, and 30 support the Faculty, Student, and Guest computers (PC1, PC2, and PC3).
How to remove one VLAN from switchport trunk?
switchport trunk allowed vlan add 30. Otherwise IOS just thinks you’re trying to overwrite the existing configuration and you are left with an accidentally deleted set of allowed VLANs. You could similarly use “remove” in place of “add” to remove only one VLAN. See the entire syntax below.
How to define the VLANs allowed on a TR?
To remove VLANs from the allowed VLANs list for a trunk, issue the clear trunk mod_num/port_num vlans command. To add specific VLANs to the allowed VLANs list for a trunk, issue the set trunk mod_num/port_num vlans command. To verify the allowed VLAN list for the trunk, issue the show trunk mod_num/port_num command.
How to add a VLAN to a Cisco switch?
You need to use the following command to add your VLAN 30 to an existing Dot1Q trunk on a Cisco Catalyst switch: Otherwise IOS just thinks you’re trying to overwrite the existing configuration and you are left with an accidentally deleted set of allowed VLANs.
Can a VLAN be added to a trunk link?
When a trunk link is established, all of the configured VLANs are allowed to send and receive traffic across the link. VLANs 1 through 1005 are allowed on each trunk by default. However, VLAN traffic can be removed from the allowed list.