ZyXEL Communications NXC2500 User Manual page 114

Chapter 8 Interfaces
Note: By default, the NXC acts a bridge device. This means all interfaces (ge1~g6) are
grouped together into a single VID, vlan0. Also note that vlan0 cannot be removed
and the VID cannot be changed.
Figure 58 Example: Before VLAN
In this example, there are two physical networks and three departments A, B, and C. The physical
networks are connected to hubs, and the hubs are connected to the router.
Alternatively, you can divide the physical networks into three VLANs.
Figure 59 Example: After VLAN
Each VLAN is a separate network with separate IP addresses, subnet masks, and gateways. Each
VLAN also has a unique identification number (ID). The ID is a 12-bit value that is stored in the
MAC header. The VLANs are connected to switches, and the switches are connected to the router.
(If one switch has enough connections for the entire network, the network does not need switches
A and B.)
• Traffic inside each VLAN is layer-2 communication (data link layer, MAC addresses). It is handled
by the switches. As a result, the new switch is required to handle traffic inside VLAN 2. Traffic is
only broadcast inside each VLAN, not each physical network.
• Traffic between VLANs (or between a VLAN and another type of network) is layer-3
communication (network layer, IP addresses). It is handled by the router.
This approach provides a few advantages.
• Increased performance - In VLAN 2, the extra switch should route traffic inside the sales
department faster than the router does. In addition, broadcasts are limited to smaller, more
logical groups of users.
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A
C
A
B
B
NXC2500 User's Guide