ZyXEL Communications 4728F User Manual

Chapter 9 VLAN

XGS-4526/4528F/4728F User’s Guide

Subnet based VLANs allow you to group traffic into logical VLANs based on the 
source IP subnet you specify. When a frame is received on a port, the Switch 
checks if a tag is added already and the IP subnet it came from. The untagged 
packets from the same IP subnet are then placed in the same subnet based VLAN. 
One advantage of using subnet based VLANs is that priority can be assigned to 
traffic from the same IP subnet.

For example, an ISP (Internet Service Provider) may divide different types of 
services it provides to customers into different IP subnets. Traffic for voice 
services is designated for IP subnet 172.16.1.0/24, video for 192.168.1.0/24 and 
data for 10.1.1.0/24. The Switch can then be configured to group incoming traffic 
based on the source IP subnet of incoming frames.

You can then configure a subnet based VLAN with priority 6 and VID of 100 for 
traffic received from IP subnet 172.16.1.0/24 (voice services). You can also have 
a subnet based VLAN with priority 5 and VID of 200 for traffic received from IP 
subnet 192.168.1.0/24 (video services). Lastly, you can configure VLAN with 
priority 3 and VID of 300 for traffic received from IP subnet 10.1.1.0/24 (data 
services). All untagged incoming frames will be classified based on their source IP 
subnet and prioritized accordingly. That is, video services receive the highest 
priority and data the lowest. 

Figure 43   Subnet Based VLAN Application Example