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DT Etherlink IV
The Mixed port is a port where tagged and untagged traffic is allowed. However, on ingress, a
default VLAN tag is assigned to untagged traffic (configured by QOS and VLAN commands), so that
all frames in the system are actually tagged. On egress frames with VLAN equal to the default VLAN
(configured with VLAN command), exit the port untagged, while to all other VLANs apply pass/block
rules set by the ALLOW command.
Mode
Default VLAN
(set with VLAN command)
ACCESS
Untagged traffic outside of the modem.
VLAN tag is added on ingress, removed
on egress.
TRUNK
Not taken into account
MIXED
Untagged traffic outside of the modem.
VLAN tag is added on ingress, removed
on egress.
Table 3.7 Access, Trunk and Mixed Mode
Etherlink_IV devices always transmit Ethernet packets over DSL or E1 interfaces with the VLAN
format. It means that data packets coming from Access ports are first transformed into Ethernet
packets with VLAN format (adding standard VLAN number and QoS priority level) and after this
transmitted over any line interface.
There is a special case when having the same MAC address on different VLANs and PBVLANs.
Normally, there should not be two devices on the network sharing the same VLAN. But IEEE 802.1Q
VLANs as well as port-based VLANs allow creating separate logical networks on one physical
network. Thus, in different VLANs or PBVLANs there could be devices sharing the same MAC
address. On Etherlink_IV, however, there is a hardware limitation preventing all VLAN+PBVLAN
combinations from having different address databases, and therefore, allowing same MAC address
to be used on all VLAN&PBVLAN combinations is possible in the modem configuration. But,
knowing which configurations are valid will allow using modems in all really vital configurations.
There are two rules.
1. For separately managed VLANs 1-8. Each VLAN has its own MAC address table, and thus
device with MAC address ABC in each of these 8 VLANs will not conflict with any device with
MAC address ABC in any other VLAN. But the limitation here is the use of port-based VLANs.
MAC address database is shared among all PBVLANs for VLAN1-8. Therefore a device with
MAC address XYZ, VLAN1, PBVLAN A, will conflict with device with MAC address XYZ, VLAN1,
PBVLAN B.
2. For all other VLANs. Here, every PBVLAN has its own MAC address table, but different VLANs
on one PBVLAN share the same database. A device with the MAC address XYZ, VLAN(any
other), PBVLAN A, will not conflict with a device having the MAC address XYZ, VLAN(any other),
PBVLAN B. But the device with the MAC address ABC, VLAN(any other), PBVLAN A, will
conflict with the device having the MAC address ABC, VLAN(any other+1), PBVLAN A.
User Manual
VLAN1-VLAN8, OTHER
(set with ALLOW command)
Not taken into account
Tagged traffic outside of the modem.
VLAN tag is not modified on egress and
ingress.
Tagged traffic outside of the modem for VLANs
not equal to default VLAN.
VLAN tag is not modified on egress and
ingress.
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