How Do I Use FTOS to Configure VLANs?


FTOS supports up to 1024 Virtual LANs (VLANs) at one time.

Before configuring VLANs, you must understand two concepts -- participation and tagging.


Participation defines the VLANs to which a port belongs. When a port is a member of a VLAN, it receives all multicast and broadcast traffic for that VLAN. Directly connected PCs, servers, and other network devices on member ports of the same VLAN can communicate with each other without going through a router. 

FTOS supports manual and automatic VLAN participation settings. You achieve automatic VLAN participation by enabling Generic VLAN Registration Protocol (GVRP). You achieve manual VLAN participation by a CLI command to configure the participation.

This example creates VLAN 22 and assigns interface 0/2 to static participation in the VLAN.

Force10(conf)#interface vlan 22
Force10(conf-if-vlan)#untagged gi 0/2
Force10(conf-if-vlan)#tagged gi 0/3


Tagging refers to the IEEE 802.1Q header that is inserted into the standard Ethernet header. When tagging is enabled, a tag header is added to the frame after the destination and source MAC addresses. This information is preserved as the frame moves through the network. The following figure illustrates the structure of a frame with a tag header. The VLAN ID is inserted in the tag header.

The tag header contains some key information used by FTOS:

  • VLAN protocol identifier, which identifies the frame as tagged according to the IEEE 802.1Q specifications (2 bytes).
  • Tag control information (TCI), which includes the VLAN ID (2 bytes total). The VLAN ID has a total of potential 4,096 values, but 0, 1, 4095, and 4096 are reserved.

Note: The insertion of the tag header into the Ethernet frame increases the size of the frame to more than the 1518 bytes specified in the IEEE 802.3 standard. Some devices that are not compliant with IEEE 802.3 might not support the larger frame size.

Information contained in the tag header allows the switch to prioritize traffic and to forward information to ports associated with a specific VLAN ID. 

This next example configures tagging on interface 0/5. With this configuration, interface 0/5 will insert a 4-byte tag in the header of all transmitted frames. It also will reclassify or assign all frames received without an existing tag to VLAN 55.

!-- Enter Global Config mode
Force10(Config)#interface vlan 55
!-- Create and/or configure VLAN 55
Force(conf-if-vl-55)#tagged 0/5
!-- Add interface 0/5 to VLAN 55 as tagged, and set
!-- PVID to 55. Also implicitly removes interface from VLAN 1

Configuration Example


s50-1(config)#interface vlan 11
s50-1(conf-if-vl-11)#untagged 0/49
s50-1(conf-if-vl-11)#untagged 0/50


s50-2(config)#interface vlan 11
s50-2(conf-if-vl-11)#untagged 0/49
s50-2(conf-if-vl-11)#untagged 0/50
s50-2#show vlan id 11
Codes: * - Default VLAN, G - GVRP VLANs, E - Ethernet interface
Codes: * - Default VLAN, G - GVRP VLANs
Q: U - Untagged, T - Tagged
x - Dot1x untagged, X - Dot1x tagged
G - GVRP tagged
 NUM   Status Description  Q Ports
-------  ---------  -  --------
11       Inactive   U  E  0/49,0/50
s50-2#show switchport gigabitethernet 0/49
Codes:  U - Untagged, T - Tagged
x - Dot1x untagged, X - Dot1x tagged
G - GVRP tagged

Name: GigabitEthernet 0/49
Description: "R1 // Customer R4"
802.1QTagged: False
Vlan membership:
Q Vlans
U 11

s50-2#show switchport gigabitethernet 0/50
Codes:  U - Untagged, T - Tagged
x - Dot1x untagged, X - Dot1x tagged
G - GVRP tagged

Name: GigabitEthernet 0/50
Description: "R4 link"
802.1QTagged: False
Vlan membership:
Q Vlans
U 11



s50-3 #configure
s50-3(Config)#interface vlan 11
s50-3 (Conf-if-vl-11)#untagged 0/49
s50-3 (Conf-if-vl-11)#untagged 0/50

Information to Collect if You Open a TAC Case

If you would like assistance from Force10 Networks after following the steps above, please use the Create Service Request form on the iSupport page and include the following information if available:

  • Console captures showing the steps taken
  • Output from the show tech-support command to capture the installed hardware and the SFTOS version
  • Network diagrams or other descriptions of the network design, including VLAN configurations and IP address ranges
  How do you rate this document ?
Not Helpful Very Helpful
Comments / Suggestions