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Add a section on lagg(4) network aggregation and failover.

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Submitted by:  Andrew Thompson (thompsa@)
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Murray Stokely 2007-09-12 11:47:33 +00:00
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Notes: svn2git 2020-12-08 03:00:23 +00:00 
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en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml
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@ -2859,6 +2859,194 @@ BEGEMOT-BRIDGE-MIB::begemotBridgeDefaultBridgeIf.0 s bridge2</screen>
</sect2>
</sect1>
<sect1 id="network-aggregation">
<sect1info>
<authorgroup>
<author>
<firstname>Andrew</firstname>
<surname>Thompson</surname>
<contrib>Written by </contrib>
</author>
</authorgroup>
</sect1info>
<title>Link Aggregation and Failover</title>
<indexterm><primary>lagg</primary></indexterm>
<indexterm><primary>failover</primary></indexterm>
<indexterm><primary>fec</primary></indexterm>
<indexterm><primary>lacp</primary></indexterm>
<indexterm><primary>loadbalance</primary></indexterm>
<indexterm><primary>roundrobin</primary></indexterm>
<sect2>
<title>Introduction</title>
<para>The &man.lagg.4; interface allows aggregation of multiple network
interfaces as one virtual interface for the purpose of providing
fault-tolerance and high-speed links.</para>
</sect2>
<sect2>
<title>Operating Modes</title>
<variablelist>
<varlistentry><term>failover</term>
<listitem>
<para>Sends and receives traffic only through the master port. If the
master port becomes unavailable, the next active port is used. The
first interface added is the master port; any interfaces added after
that are used as failover devices.</para>
</listitem>
</varlistentry>
<varlistentry><term>fec</term>
<listitem>
<para>Supports Cisco EtherChannel. This is a static setup and does not
negotiate aggregation with the peer or exchange frames to monitor the
link, if the switch supports LACP then that should be used
instead.</para>
<para>Balances outgoing traffic across the active ports based on hashed
protocol header information and accepts incoming traffic from any
active port. The hash includes the Ethernet source and destination
address, and, if available, the VLAN tag, and the IPv4/IPv6 source
and destination address.</para>
</listitem>
</varlistentry>
<varlistentry><term>lacp</term>
<listitem>
<para>Supports the IEEE 802.3ad Link Aggregation Control Protocol
(LACP) and the Marker Protocol. LACP will negotiate a set of
aggregable links with the peer in to one or more Link Aggregated
Groups. Each LAG is composed of ports of the same speed, set to
full-duplex operation. The traffic will be balanced across the ports
in the LAG with the greatest total speed, in most cases there will
only be one LAG which contains all ports. In the event of changes in
physical connectivity, Link Aggregation will quickly converge to a
new configuration.</para>
<para>Balances outgoing traffic across the active ports based on hashed
protocol header information and accepts incoming traffic from any
active port. The hash includes the Ethernet source and destination
address, and, if available, the VLAN tag, and the IPv4/IPv6 source
and destination address.</para>
</listitem>
</varlistentry>
<varlistentry><term>loadbalance</term>
<listitem>
<para>This is an alias of <emphasis>fec</emphasis> mode.</para>
</listitem>
</varlistentry>
<varlistentry><term>roundrobin</term>
<listitem>
<para>Distributes outgoing traffic using a round-robin scheduler
through all active ports and accepts incoming traffic from any active
port. This mode will violate Ethernet frame ordering and should be
used with caution.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2>
<title>Examples</title>
<example id="networking-lacp-aggregation-cisco">
<title>LACP aggregation with a Cisco switch</title>
<para>This example connects two interfaces on a &os; machine to the
switch as a single load balanced and fault tolerant link. More interfaces
can be added to increase throughput and fault tolerance. Since frame
ordering is mandatory on Ethernet links then any traffic between two
stations always flows over the same physical link limiting the maximum
speed to that of one interface. The transmit algorithm attempts to use as
much information as it can to distinguish different traffic flows and
balance across the available interfaces.</para>
<para>On the Cisco switch add the interfaces to the channel group.</para>
<screen>interface FastEthernet0/1
channel-group 1 mode active
channel-protocol lacp
!
interface FastEthernet0/2
channel-group 1 mode active
channel-protocol lacp
!</screen>
<para>On the &os; machine create the lagg interface.</para>
<screen>&prompt.root; <userinput>ifconfig lagg0 create</userinput>
&prompt.root; <userinput>ifconfig lagg0 up laggproto lacp laggport fxp0 laggport fxp1</userinput></screen>
<para>View the interface status from ifconfig; ports marked as
<emphasis>ACTIVE</emphasis> are part of the active aggregation group
that has been negotiated with the remote switch and traffic will be
transmitted and received. Use the verbose output of &man.ifconfig.8;
to view the LAG identifiers.</para>
<screen>lagg0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
options=8&lt;VLAN_MTU&gt;
ether 00:05:5d:71:8d:b8
media: Ethernet autoselect
status: active
laggproto lacp
laggport: fxp1 flags=1c&lt;ACTIVE,COLLECTING,DISTRIBUTING&gt;
laggport: fxp0 flags=1c&lt;ACTIVE,COLLECTING,DISTRIBUTING&gt;</screen>
<para>The switch will show which ports are active. For more detail use
<userinput>show lacp neighbor detail</userinput>.</para>
<screen>switch# show lacp neighbor
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
Channel group 1 neighbors
Partner's information:
LACP port Oper Port Port
Port Flags Priority Dev ID Age Key Number State
Fa0/1 SA 32768 0005.5d71.8db8 29s 0x146 0x3 0x3D
Fa0/2 SA 32768 0005.5d71.8db8 29s 0x146 0x4 0x3D</screen>
</example>
<example id="networking-lagg-failover">
<title>Failover mode</title>
<para>Failover mode can be used to switch over to another interface if
the link is lost on the master.</para>
<screen>&prompt.root; <userinput>ifconfig lagg0 create</userinput>
&prompt.root; <userinput>ifconfig lagg0 up laggproto failover laggport fxp0 laggport fxp1</userinput></screen>
<screen>lagg0: flags=8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mtu 1500
options=8&lt;VLAN_MTU&gt;
ether 00:05:5d:71:8d:b8
media: Ethernet autoselect
status: active
laggproto failover
laggport: fxp1 flags=0&lt;&gt;
laggport: fxp0 flags=5&lt;MASTER,ACTIVE&gt;</screen>
<para>Traffic will be transmitted and received on
<devicename>fxp0</devicename>. If the link is lost on
<devicename>fxp0</devicename> then <devicename>fxp1</devicename> will
become the active link. If the link is restored on the master
interface then it will once again become the active link.</para>
</example>
</sect2>
</sect1>
<sect1 id="network-diskless">
<sect1info>
<authorgroup>