2.0 CCNA - Network Access

2.1 Configure and verify VLANs (normal range) spanning multiple switches

2.1.b Default VLAN

The default VLAN is a pre-configured VLAN on a network switch that is used for untagged or unassigned network traffic. It is typically VLAN 1 and is used to carry traffic from devices that are not assigned to a specific VLAN.

In a switched network, all switch ports are assigned to a VLAN by default, typically VLAN 1. If a device is connected to a switch port that is assigned to VLAN 1, the device will be part of the default VLAN and its traffic will be sent over that VLAN.

It is generally recommended to avoid using the default VLAN for security reasons, as all untagged traffic on a switch port is part of the default VLAN. Instead, you should create and assign specific VLANs for your network devices to ensure a more secure and efficient network.

To change the default VLAN, you need to create a new VLAN and assign it to the switch ports as needed. You can also change the VLAN assignment for a specific port using the "switchport access vlan [vlan-id]" command.

2.2 Configure and verify interswitch connectivity

To configure and verify interswitch connectivity, you can follow these steps:

1. Configure trunking on both switches:
- Enter interface configuration mode for the ports that will be used for trunking using the "interface [port]" command.
- Configure the port as a trunk using the "switchport mode trunk" command.
- Configure the port as a trunk using the "switchport mode trunk" command. Specify the VLANs allowed on the trunk using the "switchport trunk allowed vlan [vlan-id]" command. Repeat these steps on both switches for the same trunk ports.

2. Verify the trunk configuration:
- Use the "show interfaces [port] switchport" command to display the trunk configuration for a specific port.
- Verify that the trunk encapsulation, allowed VLANs, and trunk status are correct.
3. Test interswitch connectivity:
- Connect a device, such as a computer, to a switch port assigned to a specific VLAN.
- Ping a device on the other switch that is also connected to the same VLAN.
- If the ping is successful, interswitch connectivity is working correctly.

Note: It's important to follow best practices for trunk configuration, such as using consistent encapsulation (e.g. IEEE 802.1Q) and ensuring the same allowed VLANs are configured on both switches. This helps to ensure that interswitch connectivity is reliable and secure.