Dell N1100-ON, Справочное руководство

Страница: 785 / 2332

Layer 2 Switching Commands
785
Double VLAN Mode
An incoming frame is identified as tagged or untagged based on Tag Protocol
Identifier (TPID) value it contains. The IEEE 802.1Q standard specifies a
TPID value (0x8100) to recognize an incoming frame as tagged or untagged.
Any valid Ethernet frame with a value of 0x8100 in the 12th and 13th bytes is
recognized as a tagged frame.
Dell EMC Networking N-Series switches can be configured to enable the port
in double-VLAN (QinQ) mode. In this mode, the switch looks for 12th, 13th,
16th, and 17th bytes for the tag status in the incoming frame. The outer tag
TPID is identified by the 12th and 13th bytes values. The inner tag TPID is
identified by 16th and 17th bytes values. These two TPID values can be
different or the same. VLAN normalization, source MAC learning, and
forwarding are based on the outer value in a received frame.
NOTE:
DVLAN is not available on the N3000 Series switches when utilizing the
AGGREGATION ROUTER image.
Independent VLAN Learning
Independent VLAN Learning (IVL) allows unicast address-to-port mappings
to be created based on a MAC Address in conjunction with a VLAN ID.
This arrangement associates the MAC Address only with the VLAN on which
the frame was received. Therefore, frames are forwarded based on their
unicast destination address as well as their VLAN membership. This
configuration affords multiple occurrences of an address in the forwarding
database. Each address associates with a unique VLAN. Care must be taken
in the administration of networks, as multiple instances of a MAC address,
each on a different VLAN, can quickly eat up address entries.
Each VLAN is associated with its own forwarding database. Hence the
number of forwarding databases equals the number of VLANs supported.
The MAC address stored is supplemented by a 2-byte VLAN ID. The first 2
bytes of a forwarding database entry contain the VLAN ID associated, and the
next 6 bytes contain the MAC address. There is a one-to-one relationship
between VLAN ID and FID (forwarding database ID).