Enabling Null Vlan As The Default Vlan - Dell S3048-ON Configuration Manual

Native VLAN support breaks this barrier so that you can connect a port to both VLAN-aware and VLAN-unaware stations. Such ports are
referred to as hybrid ports. Physical and port-channel interfaces may be hybrid ports.
Native VLAN is useful in deployments where a Layer 2 port can receive both tagged and untagged traffic on the same physical port. The
classic example is connecting a voice-over-IP (VOIP) phone and a PC to the same port of the switch. The VOIP phone is configured to
generate tagged packets (with VLAN = VOICE VLAN) and the attached PC generates untagged packets.
NOTE: When a hybrid port is untagged in a VLAN but it receives tagged traffic, all traffic is
accepted.
NOTE: You cannot configure an existing switchport or port channel interface for Native VLAN. Interfaces must have no other
Layer 2 or Layer 3 configurations when using the portmode hybrid command or a message similar to this displays: % Error:
Port is in Layer-2 mode Gi 5/6.
To configure a port so that it can be a member of an untagged and tagged VLANs, use the following commands.
1 Remove any Layer 2 or Layer 3 configurations from the interface.
INTERFACE mode
2 Configure the interface for Hybrid mode.
INTERFACE mode
portmode hybrid
3 Configure the interface for Switchport mode.
INTERFACE mode
switchport
4 Add the interface to a tagged or untagged VLAN.
VLAN INTERFACE mode
[tagged | untagged]

Enabling Null VLAN as the Default VLAN

In a Carrier Ethernet for Metro Service environment, service providers who perform frequent reconfigurations for customers with changing
requirements occasionally enable multiple interfaces, each connected to a different customer, before the interfaces are fully configured.
This presents a vulnerability because both interfaces are initially placed in the native VLAN, VLAN 1, and for that period customers are able
to access each other's networks. Dell Networking OS has a Null VLAN to eliminate this vulnerability. When you enable the Null VLAN, all
ports are placed into it by default, so even if you activate the physical ports of multiple customers, no traffic is allowed to traverse the links
until each port is place in another VLAN.
To enable Null VLAN, use the following command.
• Disable the default VLAN, so that all ports belong to the Null VLAN until configured as a member of another VLAN.
CONFIGURATION mode
default-vlan disable
Default: the default VLAN is enabled (no default-vlan disable).
Virtual LANs (VLANs) 877