Static Virtual LANs (VLANs)

Port-Based Virtual LANs (Static VLANs)

The Solution. To avoid the preceding problem, use only one cable or port trunk between the single-forwarding and multiple-forwarding database devices, and configure the link with multiple, tagged VLANs.

Switch 8000M

 

 

 

 

 

 

VLAN 1

 

 

 

 

VLAN

 

 

 

VLAN 2

 

 

 

 

PC “A”

 

 

 

 

 

 

 

 

 

 

 

 

 

1 & 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A1

 

 

C1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLAN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 & 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLAN 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLAN 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Multiple-Forwarding

Database Switch

(Routing Enabled)

PC “B”

This switch has a single forwarding database.

This switch has multiple forwarding databases.

Figure 2-9. Example of a Solution for Single-Forwarding to Multiple-Forwarding Database Devices in a Multiple VLAN Environment

Now, the 8000M forwarding database always lists the multiple-forwarding database switch MAC address on port A1, and the 8000M will send traffic to either VLAN on the multiple-forwarding database switch.

To increase the network bandwidth of the connection between the devices, you can use a trunk of multiple physical links rather than a single physical link.

Multiple-Forwarding Database Operation

If you want to connect a switch covered by this guide to another switch that has a multiple-forwarding database, you can use either 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 table 2-6.) The switches covered by this guide that use the same MAC address on all VLAN interfaces cause 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:

2-14