ZyXEL Communications XGS4700 Series, Manual

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Chapter 9 VLAN
XGS4700-48F User’s Guide
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9.6 Subnet Based VLANs
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.
Note: Subnet based VLAN applies to un-tagged packets and is applicable only when
you use IEEE 802.1Q tagged VLAN.
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 48 Subnet Based VLAN Application Example
10.1.1.0/24
192.168.1.0/24
172.16.1.0/24
Internet
VID = 100 VID = 200
VID = 300
Untagged
Frames
Tagged Frames