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NAME    [Toc]    [Back]

       vlan, VLAN - Virtual LAN (VLAN) introductory information

DESCRIPTION    [Toc]    [Back]

       A  Virtual  Local Area Network (VLAN) provides administrators
 with the ability to create logical groups of  systems
       that can communicate as if they were on the same LAN. Multiple
 VLANs can exist on the same physical network.  Traffic
 between VLANs is restricted. Bridges forward all traffic,
 including broadcast traffic,  only  to  LAN  segments
       that serve the VLAN to which the traffic belongs.

       A VLAN is identified by a VLAN ID, which is contained in a
       special Ethernet frame called a tagged frame. This tagging
       format is defined in the IEEE 802.1q standard.

       VLAN  requires  an  optional  kernel subsystem (vlan.mod).
       You can verify the presence of the VLAN subsystem by issuing
  the  sysconfig -s vlan command. If the vlan subsystem
       is not loaded, you can load it using either of the following
  methods:  Dynamically  load it using the sysconfig -c
       vlan command.  Run  the  vlanconfig  command.  This  loads
       vlan.mod if it is not present in the kernel.

       After the subsystem is loaded, you can configure a VLAN.

   VLAN Configuration    [Toc]    [Back]
       You  can  configure  VLANs  either in multiuser mode or at
       boot time with the vlanconfig command. When you  configure
       a  VLAN,  you  specify the virtual interface name (vlanx),
       the lower interface on which the VLAN virtual interface is
       configured,  and  a VLAN ID. This enables the lower interface
 to participate in the VLAN identified by the VLAN ID.
       You  can  enable  an  interface to participate in multiple
       VLANs by creating multiple virtual interfaces on  it.  The
       total number of VLAN virtual interfaces is limited only by
       system resources.

       After you create a VLAN virtual interface, you  manage  it
       like  any  interface  by  using  the ifconfig command (for
       example, to configure IP addresses).

       After an interface is  configured  for  VLAN,  all  frames
       received  on  that interface are either enqueued to a VLAN
       virtual interface, or dropped. If the received frame is an
       IEEE 802.1q tagged frame, the VLAN ID is extracted and the
       frame is delivered to the VLAN virtual interface with  the
       same  VLAN ID or is dropped if none is found. If the frame
       is not a tagged frame (that is, typical Ethernet traffic),
       it is delivered to the untagged VLAN virtual interface, or
       dropped if the untagged interface is not found. (See vlanconfig(8)  for  more  information.)  This provides maximum
       flexibility to the system manager in establishing  a  VLAN

       Packets  sent  from  a VLAN virtual interface are encapsulated
 in tagged frames that include their VLAN ID. Packets
       sent  from  an untagged VLAN virtual interface are sent as
       untagged frames. Interfaces that are  enabled  for  tagged
       frames  must  be connected to LAN segments, or directly to
       switches, that support IEEE  802.1q  tagging.  A  switch's
       VLAN configuration must be done manually.

   VLAN and NetRAIN    [Toc]    [Back]
       You  can  enable NetRAIN virtual interfaces (nr) for VLANs
       provided the physical adapters that make  up  the  NetRAIN
       set  adhere to the restrictions in the "Restrictions" section.
 Each adapter in the NetRAIN set must be connected to
       a  switch  port  that  is  configured into the same set of
       VLANs as the NetRAIN virtual interface. You cannot configure
 VLAN virtual interfaces into a NetRAIN set.

       Interfaces  in  a  NetRAIN set attempt to communicate with
       each other so that nifftmt will maintain the correct state
       for  each  interface.   If the interfaces are connected to
       switch ports that only accept and forward  tagged  frames,
       these NetRAIN internal packets will not be delivered until
       a tagged VLAN interface has been configured on the NetRAIN
       virtual  interface.   In  the interim, nifftmt will report
       the interfaces as being dead.

   VLAN and Link Aggregation    [Toc]    [Back]
       You can enable link aggregation group  virtual  interfaces
       (lag)  for  VLANs provided the physical adapters that make
       up the group adhere to the restrictions in  the  "Restrictions"
  section.  Each  adapter  in the group must be connected
 to a switch port that is configured into  the  same
       set  of VLANs as the link aggregation group virtual interface.
 You cannot configure VLAN virtual interfaces into  a
       link aggregation group.

RESTRICTIONS    [Toc]    [Back]

       The  following  restrictions apply: Supports only Ethernet
       (802.3 CSMA/CD) links.  Supports only DEGPA  (alt),  DE60x
       (ee),  DEGXA (bcm), and TULIP (tu) network interface cards
       (NICs).  VLAN virtual interfaces  copy  the  lower  interface's
  MAC  address  when  they are created. If the lower
       interface's MAC address  subsequently  changes,  the  VLAN
       interface  MAC address will not be updated. This can occur
       in the following cases: The lower interface is  a  NetRAIN
       virtual  interface  --  If  you  delete  all  members in a
       NetRAIN set and then add one interface  with  a  different
       MAC  address  to  the empty set.  The lower interface is a
       Link  Aggregation  virtual  interface  --  If  static  MAC
       addressing  is not in use and you delete the original port
       from the LAG group.

              If these cases cannot be  avoided,  then  all  VLAN
              virtual  interfaces on that lower interface must be
              deleted and recreated in order to use the  new  MAC
              address.   VLAN virtual interfaces do not currently
              support  setting  characteristics  such  as  speed,
              duplex  mode,  autonegotiation, or MAC address. Any
              required modifications to the lower interface  must
              be made before configuring a VLAN virtual interface
              on it.  VLAN  virtual  interfaces  support  setting
              their  IP  maximum transfer unit (MTU) to higher or
              lower values. If the  new  MTU  value  reduces  the
              value on the lower interface, the change is applied
              only on the VLAN virtual interface.  If the new MTU
              value  increases  the value on the lower interface,
              it is applied on both the lower interface  and  the
              VLAN virtual interface.

SEE ALSO    [Toc]    [Back]

       Commands: vlanconfig(8)

       System Attributes: sys_attrs_vlan(5)

       Files: inet.local(4)

       Technical Overview

       Network Administration: Connections

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