ZyXEL Communications RGS Series User Manual page 143

Mode
Port VLAN
Port Type
The port mode (default is Access) determines the fundamental behavior of the port in
question. A port can be in one of three modes as described below.
Whenever a particular mode is selected, the remaining fields in that row will be either
grayed out or made changeable depending on the mode in question.
Grayed out fields show the value that the port will get when the mode is applied.
Access:
Access ports are normally used to connect to end stations. Dynamic features like
Voice VLAN may add the port to more VLANs behind the scenes. Access ports have
the following characteristics:
•
Member of exactly one VLAN, the Port VLAN (a.k.a. Access VLAN), which
by default is 1
•
Accepts untagged and C-tagged frames
•
Discards all frames that are not classified to the Access VLAN
•
On egress all frames classified to the Access VLAN are transmitted
untagged. Other (dynamically added VLANs) are transmitted tagged
Trunk:
Trunk ports can carry traffic on multiple VLANs simultaneously, and are
normally used to connect to other switches. Trunk ports have the following
characteristics:
•
By default, a trunk port is member of all VLANs (1-4095)
•
The VLANs that a trunk port is member of may be limited by the use of
Allowed VLANs
•
Frames classified to a VLAN that the port is not a member of are discarded
•
By default, all frames but frames classified to the Port VLAN (a.k.a. Native
VLAN) get tagged on egress. Frames classified to the Port VLAN do not get
C-tagged on egress
•
Egress tagging can be changed to tag all frames, in which case only tagged
frames are accepted on ingress
Hybrid:
Hybrid ports resemble trunk ports in many ways, but add additional port configuration
features. In addition to the characteristics described for trunk ports, hybrid ports have
these abilities:
•
Can be configured to be VLAN tag unaware, C-tag aware, S-tag aware, or
S-custom-tag aware
•
Ingress filtering can be controlled
•
Ingress acceptance of frames and configuration of egress tagging can be
configured independently
Determines the port's VLAN ID (a.k.a. PVID). Allowed VLANs are in the range 1
through 4095, default being 1.
On ingress, frames get classified to the Port VLAN if the port is configured as VLAN
unaware, the frame is untagged, or VLAN awareness is enabled on the port, but the
frame is priority tagged (VLAN ID = 0).
On egress, frames classified to the Port VLAN do not get tagged if
configuration is set to untag Port VLAN.
The Port VLAN is called an "Access VLAN" for ports in Access mode and Native
VLAN for ports in Trunk or Hybrid mode.
Ports in hybrid mode allow for changing the port type, that is, whether a frame's VLAN
tag is used to classify the frame on ingress to a particular VLAN, and if so, which TPID
it reacts on. Likewise, on egress, the Port Type determines the TPID of the tag, if a tag
is required.
Egress Tagging
143