User guide

VLAN Functional Description VLAN
2-89
iMG/RG Software Reference Manual (Switching)
• A port can be member of two or more VLANs only if it is tagged on all the VLANs or it is untagged on one
VLAN only and tagged on all the other VLANs. A port cannot be member of two or more VLANs as
untagged port.
To change the tagged/untagged frame format of a port for a specific VLAN it's necessary remove the port from
the VLAN and then re-add the port to the VLAN, specifying the required frame format.
When a port is removed from a VLAN and the same port is not a member of any other VLAN, the port is auto-
matically added to the default VLAN with the untagged attribute.
2.4.2.2 VLAN support on ADSL interface
The ADSL Residential Gateways extend the support on tagged frames from the Ethernet ports to the ADSL
port.
Specifically, only on ADSL connections that use RFC1483 encapsulation method, it’s possible assign a connec-
tion to manage tagged traffic for one or more VLANs and simultaneously manage also untagged frames for one
VLAN only.
2.4.2.2.1 Untagged RFC1483 connections
To assign an RFC1483 to manage untagged frames for one VLAN, use the command RFC1483 SET TRANS-
PORT FRAME UNTAGGED.
• All the incoming untagged frames that from the ADSL port arrive to the residential gateway on the PVC
channel specific for the RFC1483 transport, are forwarded internally to the bridge software as tagged
frames with the VLAN identifier equal to the VID value of VLAN specified.
• If the same RFC1483 transport has not been assigned to manage any tagged frame, any tagged incoming
frames are silently discharged.
• All the outgoing tagged frames that from the bridge software must be sent outside on the ADSL port, are fil-
tered to discharge not valid tagged frames:
• If the frame VID value in the 802.1Q header equals the VID value of VLAN specified, the 802.1Q header is
removed and the frame is sent as untagged frame, otherwise the frame is silently discharged.
2.4.2.2.2 Tagged RFC1483 connections
To assign an RFC1483 to manage tagged frames for one VLAN, use the command rfc1483 set transport frame
tagged.
All the incoming tagged frames that from the ADSL port arrive to the residential gateway on the PVC channel
specific for the RFC1483 transport and having the VID value equal to the VID value of VLAN specified, are sim-
ply forwarded internally to the bridge software as tagged frames maintaining the same VLAN identifier.