Connecting the Switch to another switch with a multiple forwarding database (Example)

Use one or both of the following connection options:
  • A separate port or port trunk interface for each VLAN. This results in a forwarding database having multiple instances of the same MAC address with different VLAN IDs and port numbers. See Forwarding database content. The fact that the switches covered by this guide use the same MAC address on all VLAN interfaces causes no problems.

  • The same port or port trunk interface for multiple (tagged) VLANs. This results in a forwarding database having multiple instances of the same MAC address with different VLAN IDs, but the same port number.

Allowing multiple entries of the same MAC address on different VLANs enables topologies such as the following:

Topology for devices with multiple forwarding databases in a multiple VLAN environment