Virtual Local Area Network (VLAN) is a technology used to segment a physical network into multiple logical networks. VLANs are typically used to segment a network into different workgroups or departments. This allows each workgroup or department to have its own broadcast domain and allows for better security, as each workgroup or department is separated from the other, preventing broadcast storms or other malicious activity from spreading across departments.
VLANs are typically managed using a VLAN Trunking Protocol (VTP). VTP is a Layer 2 protocol used for managing VLANs in an Ethernet network. It allows a single VLAN database to be maintained on a VTP server, and the VTP client switches to synchronize their VLAN databases with the VTP server.
When a new VLAN is created or an existing VLAN is modified on the VTP server, the changes must be propagated to all VTP client switches in order for the changes to take effect. The process of propagating the new VLAN database to all VTP client switches is known as “forcing VTP updates”.
Forcing VTP updates can be done in one of two ways. The first method is to use the “vtp force” command on the VTP server. This command will cause the VTP server to send an update packet to all VTP client switches, which will then update their VLAN databases to match that of the VTP server.
The second method is to use the “vtp refresh” command on each VTP client switch. This command will cause the VTP client switch to request an update packet from the VTP server, which will then update its VLAN database to match that of the VTP server.
Using either of these methods will ensure that the VTP client switches are always synced up with the VTP server and that all changes made on the VTP server are propagated to the VTP client switches. This is important for ensuring that all VLANs are correctly configured and that all hosts are correctly placed into the correct VLANs.
It is also important to note that when using either of these methods, the VTP server must be configured in “transparent mode”. This will prevent the VTP server from applying any changes to the VLAN database and will only allow it to propagate the VLAN database to the VTP client switches.
In summary, forcing VTP updates is a necessary process when making changes to the VLAN database on a VTP server. It ensures that all VTP client switches have the same VLAN database and that all hosts are correctly placed into the correct VLANs. This process can be done using either the “vtp force” or “vtp refresh” commands on the VTP server or the VTP client switches, respectively. However, it is important to remember to configure the VTP server in “transparent mode” in order to prevent any changes from being applied to the VLAN database.