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IXP400 Software
Access-Layer Components: Ethernet Database (IxEthDB) API
Programmer’s Guide IXP400 Software Version 2.0 April 2005
Document Number: 252539, Revision: 007 165
ACCEPT_ALL_FRAMES or VLAN_TAGGED_FRAMES. Failure to do so will filter
all VLAN traffic except those frames tagged with VLAN ID 0.
The acceptable frame type filter can be any of the values above. Additionally, filters can be
combined (ORed) to achieve additional effects:
• Accept all frames – equivalent to accept tagged and accept untagged. Used to declare hybrid
VLAN trunks.
• Accept only untagged and priority tagged frames – equivalent to discard frames pertaining to a
VLAN. Used to declare trunks that are QoS aware but do not support VLAN.
By default all ports accept all the frame types. The frame type filter can be dynamically configured
at run time.
10.3.4.4 Ingress Tagging and Tag Removal
Each port can be associated with a default 802.1Q tag control information field, which includes the
Priority, CFI, and VLAN ID fields. Each port can be individually configured to tag all the incoming
untagged frames, remove the tag from all the incoming tagged frames, or leave the frames
unchanged.
Applying the default port 802.1Q tag to incoming untagged frames constitutes port-based VLAN
classification. Untagged Ingress frames will automatically be associated with the default port
VLAN of the port they were received on, if this feature is enabled.
Ports can be configured to remove the 802.1Q tag from the incoming frames, if the tag is present
(type/len field set to 0x8100). This feature will guarantee that no packets received from the port
will be VLAN or priority tagged, and is used to configure an 802.1Q-unaware port.
By default each port is configured in pass-through mode. When using this mode no tags are applied
or removed from the incoming frames. In this mode ports operate as hybrid VLAN trunks. Tagging
and tag removal can be dynamically configured at run time.
The NPE microcode sets the
ixp_ne_flags.vlan_en field in the IX_OSAL_MBUF to 1 on all
frames during ingress for all VLAN-enabled NPE images, or is set to 0 on all frames for all non-
VLAN-enabled NPE images. This field value is useful on egress because the NPE microcode can
use it to distinguish between regular untagged Ethernet frames and tagged frames that have Priority
0 + VLAN ID 0. The
ixp_ne_vlan_tci field value is 0 for both types of frames.
Note: The NPE cannot update the
FCS field to reflect the changes made to frames modified by ingress
tagging or tag removal. The client application should disable receive FCS appending
(ixEthAccPortRxFrameAppendFCSDisable() ), or ignore the FCS contents on received frames.
10.3.4.5 Port-Based VLAN Membership Filtering
Ports can be individually configured to define their VLAN membership status and enable VLAN
membership filtering of incoming and outgoing frames.
Port VLAN membership is a group of VLAN IDs which are allowed to be received and transmitted
on the specified port. If the port is VLAN enabled (Port VLAN ID (PVID) — not set to 0), the
minimum membership group for the port is its own PVID. Ports with no default VLAN
membership (PVID set to 0) cannot have membership groups and cannot filter frames based on
VLAN membership information. A VLAN membership group is a set of VLAN IDs to which the
port adheres to.