2.0 CCNA - Network Access

2.2 Configure and verify interswitch connectivity

Trunk ports, 802.1Q, and Native VLAN

An example of the complete configuration:

switch# configure terminal
switch(config)# interface FastEthernet0/1
switch(config-if)# switchport mode trunk
switch(config-if)# switchport trunk allowed vlan add 10,20,30
switch(config-if)# switchport trunk native vlan 1
switch(config-if)# end
switch# show interfaces FastEthernet0/1 switchport
switch# write memory

Explanation of the steps involved:

Connect to the switch using a console cable or Telnet/SSH.

1. Enter global configuration mode by typing "configure terminal"

2. Identify the interface that you want to configure as a trunk port. For example, if you want to configure interface FastEthernet0/1 as a trunk port, type "interface FastEthernet0/1".

3. Configure the interface as a trunk port by typing "switchport mode trunk".

4. Configure the allowed VLANs on the trunk port by typing "switchport trunk allowed vlan add [vlan-list]", where [vlan-list] is a comma-separated list of VLAN IDs. For example, "switchport trunk allowed vlan add 10,20,30".

5. Optionally, you can configure the native VLAN on the trunk port by typing "switchport trunk native vlan [vlan-id]", where [vlan-id] is the ID of the native VLAN.

6. Verify the trunk port configuration by typing "show interfaces [interface-name] switchport", where [interface-name] is the name of the interface you configured as a trunk port.

7. Save the configuration by typing "write memory".

Note: It's important to follow best practices for trunk configuration and ensure that the same allowed VLANs and Native VLAN are configured on both switches that are connected by a trunk. This helps to ensure that inter-VLAN communication is reliable and secure.

2.3 Configure and verify Layer 2 discovery protocols (Cisco Discovery Protocol and LLDP)

Layer 2 discovery protocols, such as Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP), allow network devices to learn about other directly connected Cisco equipment, such as switches, routers, and other devices. Here's how to configure and verify these protocols:

1. Configure CDP:
- Enter global configuration mode using the "configure terminal" command.
- Enable CDP globally using the "cdp run" command.
- Verify the CDP status using the "show cdp" command.
2. Configure LLDP:
- Enter global configuration mode using the "configure terminal" command.
- Enable LLDP globally using the "lldp run" command.
- Verify the LLDP status using the "show lldp" command.

To verify the information learned by these protocols, use the following commands:

1. CDP:
- Use the "show cdp neighbors" command to display information about directly connected CDP-enabled devices, including device type, IOS version, and local and remote interfaces.
2. LLDP:
- Use the "show lldp neighbors" command to display information about directly connected LLDP-enabled devices, including device type, IOS version, and local and remote interfaces.

Note: CDP is a proprietary protocol developed by Cisco, while LLDP is an industry-standard protocol. LLDP can be used to discover information about devices from different vendors, while CDP is limited to discovering information about Cisco devices only.