Enabling Null Vlan As The Default Vlan - Dell Z9500 Configuration Manual

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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.

Remove any Layer 2 or Layer 3 configurations from the interface.

INTERFACE mode

Configure the interface for Hybrid mode.

INTERFACE mode

portmode hybrid

Configure the interface for Switchport mode.

INTERFACE mode

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)