PBVLANs are used as a way to isolate groups of network interfaces from each other. No frames
from interface LAN2 connected to PBVLAN A will ever be forwarded to interface INT, which is
connected to PBVLAN E. And vice versa.
Each PBVLAN is a separate switching fabric. As there are 5 PBVLAN and no more than 10
network interfaces in the modem, one can connect any WAN interface to any LAN interface
exclusively, as well as create isolated LAN-LAN or LAN-INT connections. Each PBVLAN can
include from none to all interfaces. To populate PBVLAN with interfaces, just set the appropriate
PBVLAN letter for selected interfaces.
PBVLAN isolation works only in the limits of one modem. Outside the modem, there is no
information about the PBVLAN letter the frame had inside. This is the major difference with
VLANs, where the VLAN information is carried in the VLAN tag. So, it does not hurt if WAN1,
PBLAN A on one modem is connected to WAN1, PBVLAN C on another.
PBVLAN isolation also affects aggregation of WANs in MWAN (multi-WAN). Only WAN channels
from the same PBVLAN will aggregate with each other. For example, if WAN1 and WAN3 are in
PBVLAN A, and WAN2 and WAN4 are in PBVLAN B, and all WANs go in one direction, two
MWANs will be created each consisting of 2 WANs instead of 1 MWAN with 4 WANs.
Creating a PBVLAN with only LAN ports and one WAN port will allow the modem to eliminate
most software processing of frames, creating bridge connection and thus reducing frame
propagation delay. The same applies to the case when there are several WAN ports in the
PBVLAN, but they all go in the same direction. Assigning INT port to the PBVLAN with LAN and
WAN will turn on the internal Layer2 switch. This will, however, not be sensible in most of the
applications.
Most setups where LAN traffic separation is needed can be made with PBVLANs only or VLANs
only. In some setups PBVLANs way has benefits, in some the VLAN way. Mix of VLANs and
PBVLANs is also convenient in some applications. The user can select the approach.
4.6.5.68 <MODE [IF] [ACC/TRUNK/MIX]> Command
This command selects the 802.1Q VLAN mode for any LAN interface. Along with the full words
ACCESS, TRUNK and MIXED, also abbreviations can be used, for example A or ACC for
ACCESS, MIX or M for MIXED.
In ACCESS mode only untagged frames pass into (ingress) and out of (egress) the LANx port.
On ingress, frames are assigned to default VLAN tag with VID and QoS defined by QOS, VLAN
and VID commands. On egress, only frames with VLAN equal to the default VLAN of the port
(set with VLAN command) are allowed, and the VLAN tag is removed.
In TRUNK mode only tagged frames pass into and out of the LANx port. Frames are allowed to
pass on per-VLAN basis. VLANs allowed to pass are those selected with the ALLOW command
(any combination of VLAN1-8 and OTHER can be selected).
In MIXED mode tagged and untagged traffic is allowed on the port. However, on ingress, a default
VLAN tag (selected with QOS, VLAN and VID commands) is added to untagged frames so that
all frames in the system are actually tagged. On egress frames with VLAN equal to the default
VLAN (set with VLAN command) exit the port untagged, while to all other VLANs apply pass/block
rules are set by the ALLOW command.
4.6.5.69 <VLAN [IF] [1..8]> Command
This command sets default VLAN number for interfaces in ACCESS or MIXED mode ([IF] is LANx,
INT). Default VLAN is used to assign VLAN information for untagged traffic.
In ACCESS mode, only frames with VLAN equal to port's default VLAN are allowed to egress.
In MIXED mode, frames with VLAN equal to port's default VLAN egress untagged. Frames of al
other VLANs are blocked or are allowed to egress tagged according to rules set by ALLOW
command.
In both ACCESS and MIXED modes ingressing untagged frames are assigned to default VLAN.
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