100• Like a trunk port, a hybrid port can carry multiple VLANs to receive and send traffic for them. Unlikea trunk port, a hybrid port allows traffic of all VLANs to pass through VLAN untagged. You can usehybrid ports to interconnect network devices or connect to terminals.Default VLANBy default, VLAN 1 is the default VLAN for all ports. You can configure the default VLAN for a port asrequired.Use the following guidelines when configuring the default VLAN on a port:• Because an access port can join only one VLAN, its default VLAN is the VLAN to which it belongsand cannot be configured.• Because a trunk or hybrid port can join multiple VLANs, you can configure a default VLAN for theport.• You can use a nonexistent VLAN as the default VLAN for a hybrid or trunk port but not for an accessport. After you remove the VLAN that an access port resides in with the undo vlan command, thedefault VLAN of the port changes to VLAN 1. The removal of the VLAN specified as the defaultVLAN of a trunk or hybrid port, however, does not affect the default VLAN setting on the port.NOTE:• Do not set the voice VLAN as the default VLAN of a port in automatic voice VLAN assignment mode. Forinformation about voice VLAN, see the chapter "Voice VLAN configuration."• H3C recommends that you set the same default VLAN ID for the local and remote ports.• Make sure that a port is assigned to its default VLAN. Otherwise, when the port receives frames taggedwith the default VLAN ID or untagged frames (including protocol packets such as MSTP BPDUs), the portfilters out these frames.The following table shows how ports of different link types handle frames:Port type Actions (in the inbound direction) Actions (in the outbounddirection)Untagged frame Tagged frameAccess Tag the frame with thedefault VLAN tag.• Receive the frame if itsVLAN ID is the same as thedefault VLAN ID.• Drop the frame if its VLANID is different from thedefault VLAN ID.Remove the VLAN tag and sendthe frame.TrunkCheck whether thedefault VLAN is permittedon the port:• If yes, tag the framewith the default VLANtag.• If not, drop the frame.• Receive the frame if itsVLAN is carried on theport.• Drop the frame if its VLANis not carried on the port.• Remove the tag and send theframe if the frame carries thedefault VLAN tag and theport belongs to the defaultVLAN.• Send the frame withoutremoving the tag if its VLANis carried on the port but isdifferent from the defaultone.
