User guide

3-40 Packet Over SONET Module Installation and User Guide
Configuring the PoS Module
Configuring VLAN Tag Mapping Tables
The config dot1q tagmapping command provides support for VLAN ID (VID)
mapping tables. Each PoS port supports two VID tables: one table is used in the ingress
direction; the other is used in the egress direction. These tables make it possible to map
an input VID to an output VID, which can be useful in reconciling policy differences at
the boundary between the customer and the service provider. The tables also allow the
option of preserving the 802.1p priority or overwriting the priority with a configured
value.
To configure the VLAN tag mapping tables for a PoS port, use the following command:
config dot1q tagmapping <input_vlanid/output_vlanid> ports <portlist>
{egress {priority <priority>} | ingress {priority <priority>}}
The input_vlanid and output_vlanid parameters are both integers in the range from
1 to 4095 and must be separated by a slash character.
The
priority parameter is an integer in the range from 0 to 7.
Use the
egress keyword to apply the mapping of the input VLAN ID to the output
VLAN ID to frames received from the switch backplane prior to transmitting them onto
the PPP link. Use the
ingress keyword to apply the mapping to input frames received
from the PPP link. The mappings are applied after they are classified to a QoS profile.
Frames containing the VLAN ID specified in
input_vlanid are changed so that the
VLAN ID is set to the value specified in
output_vlanid before the frame is forwarded.
If you omit both the
egress and the ingress keywords, the command automatically
applies the specified mapping to the egress direction, and also applies a symmetrical
mapping (with the
input_vlanid and output_vlanid values reversed) to the ingress
direction.
These tables also give you the option of preserving the 802.1p priority or overwriting
the priority with a user-configured value. Using the
priority keyword in the
command indicates that the 802.1p priority field is to be set to the value specified in
priority. To preserve the 802.1p priority, do not enter the priority keyword and
value when using this command.
The default behavior is that the tables are initialized such that VLAN IDs are not altered
by the mapping operations, and frame priority is preserved. For example, an input
VLAN ID of n is always mapped to an output VLAN ID of n, and the 802.1p priority
field is not changed.