Default Sap On A Dot1Q Port - Alcatel-Lucent 7210 SAS M Service Manual

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Default SAP on a Dot1q Port

This feature introduces default SAP functionality on Dot1q-encapsulated ports. On a dot1q-
encapsulated port where a default SAP is configured, all packets with q-tags not matching any
explicitly defined SAPs will be assigned to this SAP. SAPs with default Dot1q encapsulation are
supported in VPLS and Epipe services. Dot1q Default SAP are not supported in VPRNs. In this
context, the character "*" indicates default which means allow through. The default SAP also
accepts untagged or priority tagged packets. A default SAP must be configured explicitly. When a
default SAP is not configured explicitly, packets not matching any explicitly defined SAPs will be
dropped.
One of the applications where this feature can be applicable is an access connection of a customer
who uses the whole port to access Layer 2 services. The internal VLAN tags are transparent to the
service provider. This can be provided by a null encapsulated port.
In this type of environment, logically two SAPs exist, a management SAP and a service SAP. The
management SAP can be created by specifying a VLAN tag which is reserved to manage the CPE.
The service SAP covers all other VLANs and behaves as a SAP on a null-encapsulated port.
There a few constraints related for the use of default SAP on a Dot1q-encapsulated port:
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Default SAPs on a QinQ Port (supported only on 7210 SAS-M devices con-
figured in access-uplink mode)
Default QinQ SAPs (notation - *.*) are used in ring ports to avoid the need to configure services
on all the intermediate nodes in the ring which are transiting the service. Default QinQ SAPs
matches all VLAN tagged traffic which is not classified into any other SAP configured on the
same port. Only one EPIPE service with default QinQ SAPs is needed for transit service traffic on
access-uplink ports. Default QinQ SAPs are allowed only on access-uplink ports and access ports.
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This type of SAP is supported only on VPLS and Epipe services and cannot be created in
IES and VPRN services as it cannot preserve VLAN tag markings.
For VPLS SAPs with STP enabled, STP listens to untagged and null-tagged BPDUs only.
All other tagged BPDUs are forwarded like other customer packets. This is the same
behavior as null-encapsulated ports.
This type of SAP is mutually exclusive with a SAP defined by explicit null encapsulation
(for example, 1/1/1:0). This avoids conflict as to which SAP untagged frames should be
associated.
IGMP snooping is not supported on a default SAP. This would require remembering
VLAN tags per hosts. By not allowing IGMP snooping of this SAP, all IGMP packets will
be transparently forwarded.
7210 SAS M Services Guide