Configuration Guide User guide

FastIron Configuration Guide 739
53-1002494-02
VLAN overview
Layer 2 port-based VLANs
On all Brocade devices, you can configure port-based VLANs. A port-based VLAN is a subset of
ports on a Brocade device that constitutes a Layer 2 broadcast domain.
By default, all the ports on a Brocade device are members of the default VLAN. Thus, all the ports
on the device constitute a single Layer 2 broadcast domain. When you configure a port-based
VLAN, the device automatically removes the ports you add to the VLAN from the default VLAN.
You can configure multiple port-based VLANs. You can configure up to 4094 port-based VLANs on a
Layer 2 switch or Layer 3 switch. On both device types, valid VLAN IDs are 1 – 4095. You can
configure up to the maximum number of VLANs within that ID range.
NOTE
VLAN IDs 4087, 4090, and 4093 are reserved for Brocade internal use only. VLAN 4094 is reserved
for use by Single STP. Also, if you are running an earlier release, VLAN IDs 4091 and 4092 may be
reserved for Brocade internal use only. If you want to use VLANs 4091 and 4092 as configurable
VLANs, you can assign them to different VLAN IDs. For more information, refer to “Assigning different
VLAN IDs to reserved VLANs 4091 and 4092” on page 767.
Each port-based VLAN can contain either tagged or untagged ports. A port cannot be a member of
more than one port-based VLAN unless the port is tagged. 802.1Q tagging allows the port to add a
four-byte tag field, which contains the VLAN ID, to each packet sent on the port. You also can
configure port-based VLANs that span multiple devices by tagging the ports within the VLAN. The
tag enables each device that receives the packet to determine the VLAN the packet belongs to.
802.1Q tagging applies only to Layer 2 VLANs, not to Layer 3 VLANs.
Because each port-based VLAN is a separate Layer 2 broadcast domain, by default each VLAN runs
a separate instance of the Spanning Tree Protocol (STP).
Layer 2 traffic is bridged within a port-based VLAN and Layer 2 broadcasts are sent to all the ports
within the VLAN.
Figure 71 shows an example of a Brocade device on which a Layer 2 port-based VLAN has been
configured.
FIGURE 71 Brocade device containing user-defined Layer 2 port-based VLAN