Dell S4820T, Configuration Manual

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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
).
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Virtual LANs (VLANs)