Vlans; Overview Of Virtual Local Area Networks (Vlans); Tagged, Untagged, And Dual-Mode Ports - Dell PowerConnect B-RX Configuration Manual

VLANs

Overview of Virtual Local Area Networks (VLANs)

Virtual Local Area Networks (VLANs) allow you to segment traffic in a network by placing ports and
interfaces into separate broadcast domains. Each broadcast domain is uniquely identified by VLAN
IDs. These broadcast domains can span multiple devices.
The device supports two types of VLANs: port-based VLANs and protocol-based VLANs. A
port-based VLAN consists of interfaces that constitutes a Layer 2 broadcast domain. By default, all
interfaces on a BigIron RX are members of the default VLAN, which is VLAN 1. Thus by default, all
interfaces on all devices on a network constitute a single Layer 2 broadcast domain. Once you
create a port-based VLAN and assign an interface to that VLAN, that interface is automatically
removed from the default VLAN if the port assigned is untagged. If the port assigned is tagged,
then the port remains as untag on the original VLAN (vlan1) and behaves as dual-mode port.

Tagged, untagged, and dual-mode ports

Interfaces assigned to port-based VLANs can be defined as untagged, tagged, and dual-mode
ports. An untagged port is a member of only one VLAN, while a tagged port can be a member of
more than one VLAN. Thus a tagged port can be a member of more than one broadcast domain.
Dual-mode ports are configured by adding one or more tagged VLANs and one untagged VLAN to a
port.
Tagged ports allow the device to add a four-byte 802.1q tag to the packet. 802.1q tagging is an
IEEE standard that allows a networking device to add information to Layer 2 packets. This
information identifies the VLAN membership of the packet, as well as the VLAN ID of the VLAN from
which the packet is sent. Furthermore, the default tag value of the 802.1q tag is 8100
(hexadecimal). This value comes from the 802.1q specification. You can change this tag value on a
global basis on device if needed to be compatible with other vendors' equipment.
Figure 21
vendor-specific. To use the tag for VLANs configured across multiple devices, make sure all the
devices support the same tag format.
BigIron RX Series Configuration Guide
53-1002253-01
shows the format of packets with and without the 802.1q tag. The tag format is
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