Brocade BigIron RX Series Configuration Guide - Manual (Page 368)

290 BigIron RX Series Configuration Guide
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VLAN configuration rules
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VLAN configuration rules
To create any type of VLAN on a device, Layer 2 forwarding must be enabled. When Layer 2
forwarding is enabled, the device becomes a switch on all ports for all non-routable protocols.
The BigIron RX can only support up to 254 independent VLAN with Layer 2 protocols.
In addition to this rule, the sections below summarize the rules for configuring VLANs.
VLAN ID range
VLAN IDs can be one of the following: 1 – 4089. IDs 4090 – 4094 are reserved for control
purposes.
Tagged VLANs
When configuring VLANs across multiple devices, you need to use tagging only if a port connecting
one of the devices to the other is a member of more than one port-based VLAN. If you are
configuring tagged VLANs across multiple devices, make sure all the devices support the same tag
format.
VLAN hierarchy
A hierarchy of VLANs exists between the Layer 2 and Layer 3 protocol-based VLANs:
• Port-based VLANs are at the lowest level of the hierarchy.
• Layer 3 protocol-based VLANs are at the highest level of the hierarchy.
As a device receives packets, the VLAN classification starts from the highest level VLAN first.
Therefore, if an interface is configured as a member of a port-based VLAN and a protocol-based
VLAN, packets coming into the interface are classified as members of the protocol-based VLAN
because that VLAN is higher in the VLAN hierarchy.
When a port in a VLAN receives a packet, the device forwards the packet based on the following
VLAN hierarchy:
• If it is a Layer 3 packet and the port is a member of a Layer 3 protocol-based VLAN for the
packet’s protocol, the device forwards the packet on all the Layer 3 protocol-based VLAN ports
that have been configured or drops the packet if the port is explicitly excluded from the
protocol VLAN.
• If the packet cannot be forwarded based on its VLAN membership types but the packet can be
forwarded at Layer 2, the device forwards the packet on all the ports within the receiving port’s
port-based VLAN.
Multiple VLAN membership rules
Given below are the membership rules for multiple VLAN:
• A port can belong to multiple, overlapping Layer 2 port-based VLANs only if the port is a tagged
port. Packets sent out of a tagged port use an 802.1q-tagged frame.
• A port can belong to multiple, unique, overlapping Layer 3 protocol-based VLANs.