Chapter 4: Web configuration
112 NS3552-8P-2S-V2 User Manual
802.1Q VLAN information (remember that the PVID is only used internally within the
industrial managed switch). Untagging is used to send packets from an 802.1Q-
compliant network device to a non-compliant network device.
Income Frame is tagged Income Frame is untagged
Leave port is tagged Frame remains tagged Tag is inserted
Leave port is untagged Tag is removed Frame remains untagged
IEEE 802.1Q tunneling (Q-in-Q)
IEEE 802.1Q tunneling (Q-in-Q) is designed for service providers carrying traffic for
multiple customers across their networks. Q-in-Q tunneling is used to maintain
customer-specific VLAN and Layer 2 protocol configurations even when different
customers use the same internal VLAN IDs. This is accomplished by inserting Service
Provider VLAN (SPVLAN) tags into the customer’s frames when they enter the service
provider’s network, and then stripping the tags when the frames leave the network.
A service provider’s customers may have specific requirements for their internal VLAN
IDs and number of VLANs supported. VLAN ranges required by different customers in
the same service-provider network might easily overlap, and traffic passing through the
infrastructure might be mixed. Assigning a unique range of VLAN IDs to each customer
would restrict customer configurations, require intensive processing of VLAN mapping
tables, and could easily exceed the maximum VLAN limit of 4096.
The industrial managed switch supports multiple VLAN tags and can therefore be used
in MAN (Metro Access Network) applications as a provider bridge, aggregating traffic
from numerous independent customer LANs into the MAN space. One of the purposes
of the provider bridge is to recognize and use VLAN tags so that the VLANs in the MAN
space can be used independent of the customers’ VLANs. This is accomplished by
adding a VLAN tag with a MAN-related VID for frames entering the MAN. When leaving
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