D-Link DGS-3426 User Manual - Page 138

Double VLANs, CEVLAN, Ether Type, Payload, Destination Address, Source Address, Service, Provider

Page 138 highlights

PVID xStack DGS-3400 Series Layer 2 Gigabit Ethernet Managed Switch The read-only field in the 802.1Q Port Table shows the current PVID assignment for each port, which may be manually assigned to a VLAN when created in the 802.1Q Port Settings table. The Switch's default is to assign all ports to the default VLAN with a VID of 1.The PVID is used by the port to tag outgoing, untagged packets, and to make filtering decisions about incoming packets. If the port is specified to accept only tagged frames - as tagging, and an untagged packet is forwarded to the port for transmission, the port will add an 802.1Q tag using the PVID to write the VID in the tag. When the packet arrives at its destination, the receiving device will use the PVID to make VLAN forwarding decisions. If the port receives a packet, and Ingress filtering is enabled, the port will compare the VID of the incoming packet to its PVID. If the two are unequal, the port will drop the packet. If the two are equal, the port will receive the packet. Double VLANs Double or Q-in-Q VLANs allow network providers to expand their VLAN configurations to place customer VLANs within a larger inclusive VLAN, which adds a new layer to the VLAN configuration. This lets large ISP's create L2 Virtual Private Networks and also create transparent LANs for their customers, which will connect two or more customer LAN points without over-complicating configurations on the client's side. Not only will over-complication be avoided, but also now the administrator has over 4000 VLANs in which over 4000 VLANs can be placed, therefore greatly expanding the VLAN network and enabling greater support of customers utilizing multiple VLANs on the network. Double VLANs are basically VLAN tags placed within existing IEEE 802.1Q VLANs which we will call SPVIDs (Service Provider VLAN IDs). These VLANs are marked by a TPID (Tagged Protocol ID), configured in hex form to be encapsulated within the VLAN tag of the packet. This identifies the packet as double-tagged and segregates it from other VLANs on the network, therefore creating a hierarchy of VLANs within a single packet. Here is an example Double VLAN tagged packet. Destination Address Source Address SPVLAN (TPID + 802.1Q CEVLAN Tag Ether Type Payload Service Provider (TPID + Customer VLAN VLAN Tag) Tag) Consider the example below: 124

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xStack DGS-3400 Series Layer 2 Gigabit Ethernet Managed Switch
124
PVID
The read-only field in the 802.1Q Port Table shows the current PVID assignment for each port,
which may be manually assigned to a VLAN when created in the 802.1Q Port Settings table. The
Switch's default is to assign all ports to the default VLAN with a VID of 1.The PVID is used by the
port to tag outgoing, untagged packets, and to make filtering decisions about incoming packets. If
the port is specified to accept only tagged frames - as tagging, and an untagged packet is
forwarded to the port for transmission, the port will add an 802.1Q tag using the PVID to write the
VID in the tag. When the packet arrives at its destination, the receiving device will use the PVID to
make VLAN forwarding decisions. If the port receives a packet, and Ingress filtering is enabled, the
port will compare the VID of the incoming packet to its PVID. If the two are unequal, the port will
drop the packet. If the two are equal, the port will receive the packet.
Double VLANs
llow network providers to expand their VLAN configurations to place customer VLANs within a
E 802.1Q VLANs which we will call SPVIDs (Service
AN
(TPID +
802.1Q
CEVLAN
Tag
Ether Type
Payload
Double or Q-in-Q VLANs a
larger inclusive VLAN, which adds a new layer to the VLAN configuration. This lets large ISP's create L2 Virtual Private
Networks and also create transparent LANs for their customers, which will connect two or more customer LAN points without
over-complicating configurations on the client's side. Not only will over-complication be avoided, but also now the administrator
has over 4000 VLANs in which over 4000 VLANs can be placed, therefore greatly expanding the VLAN network and enabling
greater support of customers utilizing multiple VLANs on the network.
Double VLANs are basically VLAN tags placed within existing IEE
Provider VLAN IDs). These VLANs are marked by a TPID (Tagged Protocol ID), configured in hex form to be encapsulated
within the VLAN tag of the packet. This identifies the packet as double-tagged and segregates it from other VLANs on the
network, therefore creating a hierarchy of VLANs within a single packet.
Here is an example Double VLAN tagged packet.
Destination Address
Source Address
SPVL
Service
Provider
VLAN Tag)
(TPID + Customer VLAN
Tag)
Consider the example below: