Technical data

Switching and Routing

Port-based VLANs can reduce the likelihood and severity of broadcast storms by reducing the number of ports

affected by a storm. In addition, for devices such as servers that can cause broadcast storms, you can add static

MAC entries for the devices and assign the static entries to a VLAN.

Each port-based VLAN maintains a separate spanning tree. (See “STP” on page 2-3.)

Changing the Tag Type

Tag type is the value that will be sent out on a packet to indicate it as tagged VLAN port. The 802.1q standard

recognizes the value of 8100 for this purpose. Other values can be assigned to this parameter but are not

recommended.

Brocade switches support 802.1q VLAN tagging. VLAN tagging is a method of identifying a packet as a member

of a VLAN. VLAN tagging enables you to configure ports on multiple switches into a single VLAN. Using tagged

VLANs can ease network management and ensures interoperability with other devices.

When a switch sends a packet that is a member of a tagged VLAN, the switch "tags" the packet to indicate its

VLAN membership. Other switches that support VLAN tagging recognize the tag and process the packet

according to its VLAN membership.

ServerIron(config)#tag-type 8100

Syntax: [no] tag-type <value>

The default <value> is 8100.

Enabling Aggregated VLAN

A larger Ethernet frame size for VLAN aggregation changes the maximum Ethernet size to 1530 bytes.

To enable a larger Ethernet frame size for VLAN aggregation, enter the following command:

ServerIron(config)# aggregated-vlan

Syntax: [no] aggregated-vlan

Use this command when you are configuring Super Aggregated VLANs.

Changing the ID of the Default VLAN

Before you change the VLAN ID for the default VLAN, ensure that the ID is not already in use. For example, if you

have already defined VLAN 10, do not try to use "10" as the new VLAN ID for the default VLAN. Valid VLAN IDs

are numbers .

When you enable port-based VLAN operation, all ports are assigned to VLAN 1 by default. As you create

additional VLANs and assign ports to them, the ports are removed from the default VLAN. All ports that you do

not assign to other VLANs remain members of default VLAN 1. This behavior ensures that all ports are always

members of at least one VLAN.

NOTE: Changing the default VLAN name does not change the properties of the default VLAN. Changing the

name allows you to use the VLAN ID "1" as a configurable VLAN.

ServerIron(config)#default-vlan-id 1001

Syntax: [no] default-vlan-id <value>

The <value> is from 1 – 4095. The default is 1.

Allowing TFTP Access Only to Clients in a Specific VLAN

You can allow TFTP access only to clients in a specific VLAN. The following example configures the device to

allow TFTP access only to clients connected to ports within port-based VLAN 40. Clients connected to ports that

are not in VLAN 40 are denied access.

ServerIron(config)#tftp client enable vlan 40