Trunk port

https://www.networkacademy.io/ccna/ethernet/vlan-trunking

Command on the interface

Switchport mode <mode>

If the both port are configure as dynamic auto, the trunk port will not form.

If VTP domain did not match on switches, it will not from the trunk port.

To check the VTP status,

Show vtp status

To change the VTP domain name,

vtp domain <domain_name>

Native VLAN did not match on both side of the link, it will not form the trunk port.

switchport trunk native vlan 100

Allowing VLAN is necessary.

switchport trunk allowed vlan 100,200

VTP troubleshooting

1. Domain Name miss match

Connects switch must have same domain name (case sensitive)

2. VTP version miss match

To verify VTP version on switch,

show vtp status

Changing the version,

vtp version <version no.>

3. VTP mode miss match (server, client, off & transparent)

VTP should be client or server

Changing mode,

VTP mode <Mode>

5. VTP password mismatch (Case sensitive)

VTP password for the connected switch should be same.

VLAN troubleshooting

1) If VLAN are same, they needed to be in same subnet

2) Switch should know about VLAN, if they are sharing through trunk port

3) Devices within a same VLAN connected with the respective port

4) MAC address table should be updated dynamically.

Content and note from by @arashDeljoo tutorials (Udemy)