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Chapter 4: Web configuration
84 NS3562-8P-2S User Manual
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
the MAN, the tag is stripped and the original VLAN tag with the customer-related VID is
again available.
This provides a tunneling mechanism to connect remote customer VLANs through a
common MAN space without interfering with the VLAN tags. All tags use EtherType
0x8100 or 0x88A8, where 0x8100 is used for customer tags and 0x88A8 is used for
service provider tags.
In cases where a given service VLAN only has two member ports on the switch, the
learning can be disabled for the particular VLAN and can therefore rely on flooding as
the forwarding mechanism between the two ports. This way, the MAC table
requirements are reduced.
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