netsys G.SHDSL.bis 3010E User Manual page 30

EXAMPLE:
Group
Enable VID
ID
1 10
2 20
3 30
4 40
5
6
7
8
PVID
"VID" is basically for grouping port interfaces. This means only group members can access the other group
members. For example, there is a VID group with LAN1, LAN3 and DSL. This means packets come from
DSL can only access to LAN1 and LAN3. Others cannot access to these group members.
"PVID" is for the EFM modem to check target packets, such as an ingress packet or an egress packet, for their
validity.
In 802.1q, the VLAN information is written into the Ethernet packet itself. Each packet carries a VLAN ID
(Virtual LAN ID), called a tag. This allows VLANs to be configured across multiple switches. Note that it's
possible for VLAN tags to be stripped by H/W and/or S/W.
When using 802.1q, four bytes are added to the Ethernet frame, of which 12 bits are used for the VLAN ID.
Theoretically, there can be up to 4096 VLANs per network.
An Ethernet packet that contains a VLAN ID is called a tagged packet. Conversely, an Ethernet packet with no
VLAN ID is called an untagged packet. Typically all packets leave untagged, unless tagged by the adapter
prior to arriving at the switch port.
Egress and Ingress Rules:
Egress rules determine which frames can be transmitted out of a port, based on the Egress List of the VLAN
associated with it. Each VLAN has an Egress List that specifies the ports out of which frames can be
forwarded, and specifies whether the frames will be transmitted as tagged or untagged frames.
Ingress rules are a means of filtering out undesired traffic on a port. When Ingress Filtering is enabled, a port
determines if a frame can be processed based on whether the port is on the Egress List of the VLAN
associated with the frame.
When an untagged packet arrives at the switch port, the switch will write a VLAN ID into the header of the
3010E/3020E/3040E G.SHDSL.bis EFM Bridge Modem User's Manual Ver:A2
MGM
T
LAN1 LAN2
20 30
30
Port
LAN3 LAN4 DSL
40
S-VLAN Tunnel
TPI
Mode VID
D