Application Guide

[184]
Software User's
Manual
–
Version 3.0
Note: If the Custom S-port is configured to accept Tagged and Untagged
frames (see Ingress Acceptance below), frames with a C-tag are treated like
frames with a custom S-tag.
If the Custom S-port is configured to accept Untagged Only frames, custom S-
tagged frames will be discarded (except for priority custom S-tagged frames).
C-tagged frames are initially considered untagged and will therefore not be
discarded. Later on in the ingress classification process, they will get classified
to the VLAN embedded in the tag instead of the port VLAN ID.
Ingress
Filtering
Hybrid ports allow for changing ingress filtering. Access and Trunk ports always
have ingress filtering enabled.
If ingress filtering is enabled (checkbox is checked), frames classified to a
VLAN that the port is not a member of get discarded.
If ingress filtering is disabled, frames classified to a VLAN that the port is not a
member of are accepted and forwarded to the switch engine. However, the port
will never transmit frames classified to VLANs that it is not a member of.
Ingress
Acceptance
Hybrid ports allow for changing the type of frames that are accepted on ingress.
Tagged and Untagged: Both tagged and untagged frames are accepted. See
Port Type for a description of when a frame is considered tagged.
Tagged Only: Only frames tagged with the corresponding Port Type tag are
accepted on ingress.
Untagged Only: Only untagged frames are accepted on ingress. See Port
Type for a description of when a frame is considered untagged.
Egress
Tagging
Ports in Trunk and Hybrid mode may control the tagging of frames on egress.
Untag Port VLAN: Frames classified to the Port VLAN are transmitted
untagged. Other frames are transmitted with the relevant tag.
Tag All: All frames, whether classified to the Port VLAN or not, are transmitted
with a tag.
Untag All: All frames, whether classified to the Port VLAN or not, are
transmitted without a tag. This option is only available for ports in Hybrid mode.
Allowed
VLANs
Ports in Trunk and Hybrid mode may control which VLANs they are allowed to
become members of. Access ports can only be a member of one VLAN – the
Access VLAN.
The field’s syntax is identical to the syntax used in the Enabled VLANs field. By
default, a Trunk or Hybrid port will become member of all VLANs, and is
therefore set to 1-4095.
The field may be left empty, which means that the port will not become a
member of any VLANs.
Forbidden
VLANs
A port may be configured to never become a member of one or more VLANs.
This is particularly useful when dynamic VLAN protocols like MVRP and GVRP
must be preve
nted from dynamically adding ports to VLANs.