SMC Networks SMC TigerAccess SMC7824M/FSW - Manual (Page 279)

C
ONFIGURING
IEEE 802.1Q T
UNNELING
12-21
4. After successful source and destination lookup, the packet is double
tagged. The switch uses the TPID of 0x8100 to indicate that an
incoming packet is double-tagged. If the outer tag of an incoming
double-tagged packet is equal to the port TPID and the inner tag is
0x8100, it is treated as a double-tagged packet. If a single-tagged packet
has 0x8100 as its TPID, and port TPID is not 0x8100, a new VLAN
tag is added and it is also treated as double-tagged packet.
5. If the destination address lookup fails, the packet is sent to all member
ports of the outer tag's VLAN.
6. After packet classification, the packet is written to memory for
processing as a single-tagged or double-tagged packet.
7. The switch sends the packet to the proper egress port.
8. If the egress port is an untagged member of the SPVLAN, the outer
tag will be stripped. If it is a tagged member, the outgoing packet will
have two tags.
Configuration Limitations for QinQ
• The native VLAN of uplink ports should not be used as the SPVLAN.
If the SPVLAN is the uplink port's native VLAN, the uplink port must
be an untagged member of the SPVLAN. Then the outer SPVLAN tag
will be stripped when the packets are sent out. Another reason is that it
causes none-customer packets will be forwarded to SPVLAN.
• Static trunk port groups are compatible with QinQ tunnel ports as long
as the QinQ configuration is consistent within a trunk port group.
• QinQ and L2MPLS mode cannot be supported at the same time.
• The native VLAN (VLAN 1) is not normally added to transmitted
frames. Avoiding using VLAN 1 as an SPVLAN tag for customer traffic
to reduce the risk of misconfiguration. Instead, use VLAN 1 as a
management VLAN instead of a data VLAN in the service provider
network.
• There are some inherent incompatibilities between Layer 2 and Layer 3
switching:
- A tunnel port cannot be a routed port.