ADTRAN Total Access 1240 - Manual (Page 19)

Section 2, Application Guidelines - VLAN Operation
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VLAN OPERATION
A VLAN is a switched network that is logically segmented by function, project team, or appli-
cation, without regard to the physical locations of the customers. Providers that offer multiple
services can utilize several unique VLANs with different services such as one VLAN to provide
Internet access, one VLAN to provide a Public Switched Telephone Network (PSTN), and
several other VLANs to provide data and voice services such as Voice over IP, online games, TV
broadcasting, etc.
The bridge function of the Total Access 1240 provides support for Virtual LANs in order to
create multiple domains in which packets are forwarded. This restricts traffic so that it
remains within the VLAN in which it belongs. All the learning and forwarding in the bridge is
carried out in the context of a VLAN.
The packets within the VLAN are forwarded pursuant to the following:
• Subscriber Side – Ingress
– Condition: The packet has a VLAN tag that is associated with the VC from which the
packet was received.
- The packet is forwarded to the Network Egress point.
– Condition: The packet has a VLAN tag that is inconsistent with the VC from which the
packet was received.
- The packet is discarded.
– Condition: The packet has no VLAN tag.
- The DSLAM tags the packet with the configured VLAN ID and VLAN priority for that
VC.
- The packet is forwarded to the Network Egress point.
• Network Side – Ingress
– Condition: The packet has a VLAN tag that matches one of the VLANs provisioned within
the DSLAM. The DSLAM supports up to 96 individual VLANs.
- The packet is forwarded to the corresponding customer VC egress point.
- When multiple VCs are on the same VLAN, the Total Access 1240 system matches the
packet’s MAC address to those in the MAC Learning Table and forward the packet to
the VC associated with a matching MAC address.
- If there is no corresponding MAC address in the MAC Learning Table, the packet is
forwarded to all VCs on the same VLAN in an attempt to learn the appropriate VC to
which the MAC belongs.
– Condition: The packet has a VLAN tag that does not match one of the VLANs provisioned
within the DSLAM. The DSLAM supports up to 96 individual VLANs.
- The packet is discarded.
– Condition: The packet is untagged.
- If one or more VCs are set to a VLAN of 1 (Native Operation) the Total Access 1240
system matches the packet’s MAC address to those in the MAC Learning Table and
forward the packet to the VC associated with a matching MAC address.
- If no VCs are set to Native Operation, the packet is discarded.