Zhone zNID-GPON-2402, Configuration Manual

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Configuration
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zNID 24xx Series Configuration Guide
Tagged uplink port untagged LAN ports
The diagram below shows an example of a VLAN tag (C-2) being added to
the Ethernet frame received on the LAN port. In this case the VLAN tag
remains on the frame as it is sent to the network, on the port that has been
designated as the Uplink port. Typically, this is the fiber port. Traffic that is
received from the network is expected to have the C-2 VLAN tag. This tag
will be removed before the Ethernet frame is sent to the LAN port.
Figure 156: Tagged uplink, untagged LAN ports
This is the most common configuration of the zNID 24xx. The MXK expects
tagged traffic on the uplink, while most PCs and set top boxes only use
untagged traffic.
The VLAN configuration web page shows an example of the uplink port
being tagged and the LAN ports being untagged. This is the standard
configuration when connected to an MXK.
If a tagged frame is received on the LAN port, it will be forwarded upstream
unmodified. However, in the downstream direction the VLAN tag will be
removed before sending the frame out the LAN port. This could lead to
undesirable results, since the device sending tagged frames probably expects
to receive tagged frames.