THOMSON R7.4, Configuration Manual

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E-DOC-CTC-20080229-0001 v1.0
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4| Ethernet Bridge and VLANs
4.5 Optional Incoming Traffic Validation
Introduction
The Ethernet bridge can be configured to explicitly control the handling of unexpected frames coming in on
any of its bridge ports. Unexpected frames are for example untagged frames or tagged frames coming in on
an incorrect bridge port.
Following concepts can be used to control unexpected frames:
Port VID (PVID)
Acceptable frame types
Ingress filtering
Each of these concepts is configurable per bridge port using the command
:eth bridge ifconfig
.
Port VID (PVID)
Each bridge port is configured with the
vlan
parameter, also referred to as the port VID (PVID). All untagged
and priority-tagged (VID = 0) frames received on that port are handled as if they belong to that VLAN.
The PVID must be a VLAN of which the bridge port is untagged member , as it is not possible to be tagged and
untagged member of the same VLAN. This parameter is mandatory and this is the main reason why each
bridge port has to be untagged member of at least one VLAN.
By default, the PVID of a bridge port is the default VLAN. To modify this configuration, execute following
command:
Acceptable frame types
Each bridge port can be configured with the
acceptvlanonly
parameter. This parameter is used to check
the frame format of ingress traffic:
If the parameter is disabled , both VLAN-tagged and non VLAN-tagged frames (i.e. untagged or priority-
tagged frames) are allowed on the port. Non VLAN-tagged frames are mapped to the VLAN that
corresponds with the PVID.
If the parameter is enabled , only VLAN-tagged frames are allowed. Non VLAN-tagged frames are
dropped.
By default, the parameter is disabled. To enable this parameter, execute following command:
=>:eth bridge ifconfig intf=ethport1 vlan=video
As the OBC is untagged member of maximum one VLAN (the default VLAN) and the PVID must be
a VLAN of which the port is untagged member, the PVID of the OBC is always the default VLAN.
Be careful when modifying the PVID of a bridge port. A violation of the rule that the bridge port
must be untagged member of the PVID VLAN is not always reported by the Thomson Gateway.
=>:eth bridge ifconfig intf=ethport1 acceptvlanonly=enabled