Dynamic Port Assignment (Layer 2 Switches And Layer 3 Switches); Assigning A Different Vlan Id To The Default Vlan; Assigning Trunk Group Ports; Configuring Port-Based Vlans - Foundry Networks FESX Manual

If your ISR design requires that you switch IP, IPX, or Appletalk at Layer 2 while simultaneously routing the same
protocols over a single backbone, then create multiple port-based VLANs and use VLAN tagging on the backbone
links to separate your Layer 2 switched and Layer 3 routed networks.
There is a separate STP domain for each port-based VLAN. Routing occurs independently across port-based
VLANs or STP domains. You can define each end of each backbone link as a separate tagged port-based VLAN.
Routing will occur independently across the port-based VLANs. Because each port-based VLAN's STP domain is
a single point-to-point backbone connection, you are guaranteed to never have an STP loop. STP will never block
the virtual router interfaces within the tagged port-based VLAN, and you will have a fully routed backbone.

Dynamic Port Assignment (Layer 2 Switches and Layer 3 Switches)

All Switch ports are dynamically assigned to any Layer 3 VLAN on Foundry Layer 2 Switches and any non-
routable VLAN on Foundry Layer 3 Switches. To maintain explicit control of the VLAN, you can explicitly exclude
ports when configuring any Layer 3 VLAN on a Foundry Layer 2 Switch or any non-routable Layer 3 VLAN on a
Foundry Layer 3 Switch.
If you do not want the ports to have dynamic membership, you can add them statically. This eliminates the need to
explicitly exclude the ports that you do not want to participate in a particular Layer 3 VLAN.

Assigning a Different VLAN ID to the Default VLAN

When you enable port-based VLANs, all ports in the system are added to the default VLAN. By default, the
default VLAN ID is "VLAN 1". The default VLAN is not configurable. If you want to use the VLAN ID "VLAN 1" as
a configurable VLAN, you can assign a different VLAN ID to the default VLAN.
To reassign the default VLAN to a different VLAN ID, enter the following command:
FastIron SuperX Router(config)# default-vlan-id 4095
Syntax: [no] default-vlan-d <vlan-id>
You must specify a valid VLAN ID that 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 from 1 – 4096.
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.

Assigning Trunk Group Ports

When a "lead" trunk group port is assigned to a VLAN, all other members of the trunk group are automatically
added to that VLAN. A lead port is the first port of a trunk group port range; for example, "1" in 1 – 4 or "5" in
5 – 8. See "Trunk Group Rules" on page 10-3 for more information.

Configuring Port-Based VLANs

Port-based VLANs allow you to provide separate spanning tree protocol (STP) domains or broadcast domains on
a port-by-port basis.
This section describes how to perform the following tasks for port-based VLANs using the CLI:
• Create a VLAN
• Delete a VLAN
• Modify a VLAN
• Change a VLAN's priority
• Enable or disable STP on the VLAN
December 2005 © Foundry Networks, Inc.
Configuring Virtual LANs (VLANs)
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