[networking-guide] master: Introduction to VLANs (846b7cd)

[stephenw at fedoraproject.org]

Repository : http://git.fedorahosted.org/cgit/docs/networking-guide.git

On branch  : master

>---------------------------------------------------------------

commit 846b7cd2aac70fcb8895f835170434d4e37b2ce9
Author: Stephen Wadeley <swadeley at redhat.com>
Date:   Thu Dec 18 22:35:24 2014 +0100

    Introduction to VLANs


>---------------------------------------------------------------

 en-US/Configure_802_1Q_VLAN_Tagging.xml |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/en-US/Configure_802_1Q_VLAN_Tagging.xml b/en-US/Configure_802_1Q_VLAN_Tagging.xml
index 47b22ab..f6bdd43 100644
--- a/en-US/Configure_802_1Q_VLAN_Tagging.xml
+++ b/en-US/Configure_802_1Q_VLAN_Tagging.xml
@@ -7,6 +7,33 @@
 
   <!--Topic, Tasks-->
   <title>Configure 802.1Q VLAN tagging</title>
+  <para>
+    To create a VLAN, an interface is created on another interface referred to as the <firstterm>parent interface</firstterm>. The VLAN interface will tag packets with the VLAN ID as they pass through the interface, and returning packets will be untagged. VLAN interface can be configured similarly to any other interface. The parent interface need not be an Ethernet interface. An 802.1Q VLAN tagging interface can be created on bridge, bond, and team interfaces, however there are some things to note:
+  </para>
+ 
+ <itemizedlist>
+ <listitem>
+   <para>
+ In the case of VLANs over bonds, it is important that the bond has slaves and that they are <quote>up</quote> before bringing up the VLAN interface. At the time of writing, adding a VLAN interface to a bond without slaves does not work.    
+   </para>
+ </listitem>
+ <listitem>
+   <para>
+A VLAN slave cannot be configured on a bond with the <option>fail_over_mac=follow</option> option, because the VLAN virtual device cannot change its MAC address to match the parent's new MAC address. In such a case, traffic would still be sent with the now incorrect source MAC address.</para>
+ </listitem>
+ <listitem>
+<para>
+  Sending VLAN tagged packets through a network switch requires configuration of the switch. Refer to the documentation for the switch. For example, for Cisco switches the port must be assigned to one VLAN or configured to be a trunk port to accept tagged packets for multiple VLANs. Untagged packets can also be processed by a trunk port and processed as belonging to the <firstterm>native VLAN</firstterm>, however this is a security risk and may have been disabled, or by default not enabled, depending on the make of the switch.
+</para>
+</listitem>
+
+<listitem>
+<para>
+Some older network interface cards, loopback interfaces, Wimax cards, and some InfiniBand devices, are said to be <firstterm>VLAN challenged</firstterm>, meaning they cannot support VLANs. This is usually because the devices cannot cope with VLAN headers and the larger MTU size associated with tagged packets.
+</para>
+</listitem>
+</itemizedlist>
+
 <section id="sec-Selecting_VLAN_Interface_Configuration_Methods">
 <title>Selecting VLAN Interface Configuration Methods</title>
   <itemizedlist>