This chapter covers these topics:
l
Link
Aggregation
l
Approaches
to Link Aggregation
l
Load
Sharing in a Link Aggregation Group
l
Service
Loop Group
l
Aggregation
Port Group
1.1 Link Aggregation
Link aggregation allows you to increase
bandwidth by distributing traffic on the member ports in an aggregation group.
In addition, it provides reliable connectivity because these member ports can
dynamically back up each other.
1.1.1 LACP
Link Aggregation Control Protocol (LACP) is
defined in IEEE 802.3ad. Link aggregation control protocol data
unit (LACPDU) is used for exchanging information among LACP-enabled devices.
After LACP is enabled on a port, the port
sends LACPDUs to notify the remote system of its system LACP priority, system
MAC address, port LACP priority, port number, and operational key. Upon receipt
of an LACPDU, the remote system compares the received information with the
information received on other ports to determine the ports that can operate as
selected ports. This allows the two systems to reach agreement on the states of
the related ports
When aggregating ports, link aggregation
control automatically assigns each port an operational key based on its rate,
duplex mode, and other basic configurations. In an LACP aggregation group, all
ports share the same operational key; in a manual or static LACP aggregation,
the selected ports share the same operational key.
1.1.2 Consistency Considerations for Ports
in an Aggregation
To participate in traffic sharing, member
ports in an aggregation group must use the same configurations with respect to
STP, QoS, GVRP, Q-in-Q, BPDU tunnel, VLAN, port attributes, MAC address
learning, and so on as shown in the following table.
Table 1-1
Consistency considerations for ports in an
aggregation
|
Category
|
Considerations
|
|
STP
|
State of port-level STP (enabled or
disabled)
Attribute of the link (point-to-point or
otherwise) connected to the port
Port path cost
STP priority
Maximum transmission rate
Loop protection
Root protection
Port type (whether the port is an edge
port)
|
|
QoS
|
Traffic policing
Port rate limiting
Strict priority (SP) queuing
Weighted round robin (WRR) queuing
Port priority
Policy setting on the port
Port trust mode
|
|
GVRP
|
GVRP state on ports (enabled or disabled)
GVRP registration type
GARP timers
|
|
Q-in-Q
|
State of Q-in-Q (enabled or disabled)
Added outer VLAN tag
Policy of appending outer VLAN tag according
to inner VLAN IDs
|
|
BPDU tunnel
|
BPDU tunnel state on ports (enabled or
disabled)
BPDU tunnel state for STP on ports
(enabled or disabled)
|
|
VLAN
|
VLANs carried on the port
Default VLAN ID on the port
Link type of the port, which can be
trunk, hybrid, or access
sub-net VLAN configuration
protocol VLAN configuration
VLAN tag configuration
|
|
Port attribute
|
Port rate
Duplex mode
Up/down state of the link
Isolation group membership of the port
|
|
MAC address learning
|
Maximum number of MAC addresses that can
be learned on the port
|
1.2 Approaches to
Link Aggregation
Two ways are
available for implementing link aggregation, as described in Manual Link Aggregation
and Static LACP link aggregation.
1.2.1 Manual Link Aggregation
I. Overview
Manual aggregations are created manually.
Member ports in a manual aggregation are LACP-disabled.
II. Port states in a manual
aggregation
In a manual aggregation group, ports are either
selected or unselected. Selected ports can receive and transmit data frames
whereas unselected ones cannot.
When setting the state of ports in a manual
aggregation group, the system considers the following:
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The system selects the port with the highest
priority in the up state as the reference port of the aggregation group. Port
priority descends in the following order: full duplex/high speed, full
duplex/low speed, half duplex/high speed, and half duplex/low speed. If multiple
ports are of the same priority, the one with the lowest port number is the
reference port.
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Ports in the up state with the same speed,
duplex mode, link state, and basic configuration as the reference port become
the candidates for selected ports, while the other ports become unselected
ports.
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There is a limit on the number of selected ports
in a manual aggregation group. If the number of selected-port candidates does
not reach the limit, all the candidates become selected ports; if the number of
candidates exceeds the limit, the candidates with lower port numbers become
selected ports, while the other candidates become unselected ports.
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The selected port with the lowest port number
serves as the master port of the aggregation group, and the other ports serve
as the member ports of the aggregation group.
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If all the ports of an aggregations port are
down, the port with the lowest port number is the master port. In this case,
all of them are unselected ports.
In addition, unless the master port should be
selected, a port that joins the group after the limit is reached will not be
placed in selected state even if it should be in normal cases. This is to
prevent the ongoing service on selected ports from being interrupted. You need
to avoid the situation however as the selected/unselected state of a port may
become different after a reboot.
III. Port Configuration Considerations
in manual aggregation
As mentioned above, in a manual aggregation
group, only ports with configurations consistent with those of the reference
port can become selected. These configurations include port rate, duplex mode,
link state, and other basic configurations, as described in Consistency Considerations for Ports
in an Aggregation.
You need to maintain the basic
configurations of these ports manually to ensure consistency. As one
configuration change may involve multiple ports, this can become troublesome if
you need to do that port by port. As a solution, you may add the ports into an
aggregation port group where you can make configuration for all member ports.
When the configuration of some port in a
manual aggregation group changes, the system does not remove the aggregation;
instead, it re-sets the selected/unselected state of the member ports and
re-selects a master port.
1.2.2 Static LACP link aggregation
I. Overview
Static aggregations are created manually.
After you add a port to a static aggregation, LACP is enabled on it
automatically.
II. Port states in static
aggregation
In a static aggregation group, ports can be
selected or unselected, where both can receive and transmit LACPDUs but only
selected ports can receive and transmit data frames.
When setting the state of the ports in the
local and remote static aggregation groups, the local and remote systems do the
following:
1)
Compare their system IDs to identify the higher
priority system. (The system ID comprises LACP priority and system MAC
address.)
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First compare the system LACP priorities. The
system with lower system LACP priority wins out.
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If the system LACP priorities are the same,
compare the system MAC addresses. The system with the smaller MAC address wins
out.
2)
Compare the port IDs on the higher priority
system. (The port ID comprises port LACP priority and port number.)
l
Compare the port LACP priorities. The port with
lower port LACP priority wins out.
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If two ports with the same port LACP priority
are present, compare their port numbers. The one with the smaller port ID wins
out to become the reference port.
3)
Select the candidates for selected ports. To be
a candidate, a port must be in the up state with the same speed, duplex mode,
link state, and basic configuration as the reference port; in addition, their
peer ports on the other system must have the same configuration. All the ports
but the selected-port candidates become unselected.
4)
As there is a limit on the number of selected
ports, not all selected-port candidates can become selected ports. Before the
limit is reached, all the candidates are set to the selected state. When the
limit is reached, the candidates with lower port numbers are set to the
selected state while the other candidates are set to the unselected state. At
the same time, the other system gets aware of the state change of the ports on
the higher priority system and thus sets the state of the corresponding local
ports.
5)
Set the selected port with the lowest port
number as the master port in the aggregation group on each system.
III. Port configuration
considerations in static aggregation
Like in a manual aggregation group, in a
static LACP aggregation group, only ports with configurations consistent with
those of the reference port can become selected. These configurations include
port rate, duplex mode, link state and other basic configurations described in Consistency Considerations for Ports
in an Aggregation.
You need to maintain the basic
configurations of these ports manually to ensure consistency. As one
configuration change may involve multiple ports, this can become troublesome if
you need to do that port by port. As a solution, you may add the ports into an
aggregation port group where you can make configuration for all member ports.
When the configuration of some port in a
static aggregation group changes, the system does not remove the aggregation;
instead, it re-sets the selected/unselected state of the member ports and
re-selects a master port.
1.3 Load Sharing in a Link Aggregation
Group
Link aggregation groups fall into load
sharing aggregation groups and non-load sharing aggregation groups depending on
their support to load sharing.
A load sharing aggregation group can
contain at least one selected port but a non-load sharing aggregation group can
contain only one.
Link aggregation groups perform load
sharing depending on availability of hardware resources. When hardware
resources are available, link aggregation groups created containing at least
two selected ports perform load sharing, while link aggregation groups created
with only one selected port does not perform load sharing. After hardware
resources become depleted, link aggregation groups created work in non-load
sharing mode.
Load sharing is implemented through the
selected ports in an aggregation group. However, the way of selecting
forwarding ports varies by packet type:
l
For a Layer-2 unicast packet with a known
destination MAC address, if the packet carries an IP datagram, the switch
selects the forwarding port according to the source IP address and destination
IP address; otherwise, the switch selects the forwarding port according to the source
MAC address and destination MAC address.
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For a unicast IP packet with a known destination
IP address, the switch selects the forwarding port according to the source IP
address and the destination IP address of the packet.
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For a Layer-2 multicast packet with a known
destination MAC address, the switch selects the forwarding port according to
the source MAC address, the destination MAC address, and the receiving port of
the packet.
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For a Layer-3 multicast packet with a known IP
address, the switch selects the forwarding port according to the source IP
address, the destination IP address, and the receiving port of the packet.
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For an unknown unicast/multicast/broadcast
packet, the switch selects the forwarding port according to the source MAC
address, the destination MAC address, and the receiving port of the packet.
When only one
selected port remains in a load sharing aggregation group, the group keeps
working in the load sharing mode.
1.4
Service Loop Group
You can create a service loop group by
creating a manual aggregation group of service-loop ports first and then
specifying which services can be redirected for the group. At present, you may
specify to redirect four types of services, IPv6 (IPv6 unicast), IPv6mc (IPv6
multicast), tunnel, and MPLS.
Currently, the S5500-EI
series Ethernet switches support to redirect tunnel services only.
After creating a service-loop group, assign
ports that support its service type to the group considering the following:
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These ports can be configured only with the
physical configuration such as speed and duplex mode, QoS, and ACL. Other
conflicting configurations, such as STP cannot be configured.
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These ports must belong to VLAN 1.
After
assigning a port to a service-loop group, you may configure it with other
non-conflicting settings, such as QoS.
If this
group is performing load sharing, it continues to function in this way even
after all selected ports but one are removed to ensure ongoing service.
1.5 Aggregation Port Group
As mentioned earlier, in a manual or static
aggregation group, a port can be selected only when its configuration is the
same as that of the reference port in terms of duplex/speed pair, link state,
and other basic configurations. Their configuration consistency requires
administrative maintenance, which is troublesome after you change some
configuration.
To simplify configuration, port-groups are
provided allowing you to configure for all ports in individual groups at one
time. One example of port-groups is aggregation port group.
Upon creation or removal of a link
aggregation group, an aggregation port-group which cannot be administratively
created or removed is automatically created or removed. In addition, you can
only assign/remove a member port to/from an aggregation port-group by
assigning/removing it from the corresponding link aggregation group.
For
more information about port-groups, refer to Port Correlation Configuration.
When configuring link aggregation, go to
these sections for information you are interested in:
l
Configuring
Link Aggregation
l
Displaying
and Maintaining Link Aggregation
l
Link
Aggregation Configuration Example
2.1 Configuring Link Aggregation
This section covers these topics:
l
Configuring
a Manual Link Aggregation Group
l
Configuring
a Static LACP Link Aggregation Group
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Configuring
an Aggregation Group Name
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Configuring
a Service Loop Group
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Entering
Aggregation Port Group View
2.1.1 Configuring a Manual Link Aggregation Group
Follow these steps to create a manual
aggregation group and add an Ethernet port to it:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
––
|
|
Create a manual aggregation group
|
link-aggregation group agg-id mode manual
|
Required
|
|
Enter Ethernet port view
|
interface interface-type interface-number
|
––
|
|
Assign the Ethernet port to the
aggregation group
|
port
link-aggregation group agg-id
|
Required
|
Note that:
l
You can create a manual aggregation group by
changing the type of an existing static aggregation group. When you create a
manual aggregation group in this way and the static aggregation group contains
ports, LACP is disabled on the ports after the manual aggregation group is
created.
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An aggregation group cannot contain the
following ports: RRPP-enabled ports, ports configured with static MAC addresses
or black hole MAC addresses, voice VLAN-enabled ports, or 802.1x-enabled ports.
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After you remove a manual aggregation group, all
the ports in the group are dismissed from it.
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For a manual aggregation group containing only
one port, the only way to remove the port from it is to remove the aggregation group.
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To make an aggregation group to function
properly, make sure the selected states of the ports on the both sides of the same
link are the same.
2.1.2 Configuring a Static LACP Link Aggregation Group
Follow these steps to configure a static
aggregation group:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
––
|
|
Configure the system LACP priority
|
lacp system-priority system-priority
|
Optional
32768 by default.
Changing system LACP priority can affect
the selected/unselected state of the ports in the group.
|
|
Create a static LACP aggregation group
|
link-aggregation group agg-id mode static
|
Required
|
|
Enter Ethernet port view
|
interface interface-type interface-number
|
––
|
|
Configure the port LACP priority
|
lacp port-priority
port-priority
|
Optional
32768 by default.
Changing port LACP priority can affect
the selected/unselected state of the ports in the group.
|
|
Assign the Ethernet port to the
aggregation group
|
port
link-aggregation group agg-id
|
Required
|
Note that:
l
You can create a static aggregation group by
changing the type of an existing manual link aggregation group that contains no
port.
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An aggregation group cannot contain the
following ports: RRPP-enabled ports, ports configured with static MAC addresses
or black hole MAC addresses, voice VLAN-enabled ports, or 802.1x-enabled ports.
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After you remove a static aggregation group, all
the ports in the group are dismissed from it, and LACP is disabled on the
ports.
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For a static LACP aggregation group containing
only one port, the only way to remove the port from the aggregation group is to
remove the aggregation group.
When making configuration, be aware that after a load-balancing
aggregation group changes to a non-load balancing group due to resources
exhaustion, either of the following may happen:
l
Forwarding anomaly resulted from inconsistency
of the two ends in the number of selected ports.
l
Some protocols such as GVRP malfunction because
the state of the remote port connected to the master port is unselected.
2.1.3 Configuring an Aggregation Group Name
Follow these steps to configure a name for
an aggregation group:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
––
|
|
Configure a name for a link aggregation
group
|
link-aggregation group agg-id description agg-name
|
Required
None is
configured by default.
|
2.1.4 Configuring a Service Loop Group
Follow these steps to configure a service
loop group:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
––
|
|
Create a manual aggregation group
|
link-aggregation group agg-id mode manual
|
Required
|
|
Specify the aggregation group as a
service loop group that is of specific type
|
link-aggregation group agg-id service-type tunnel
|
Required
|
|
Enter Ethernet port view
|
interface interface-type interface-number
|
––
|
|
Add the Ethernet port to the aggregation
group
|
port
link-aggregation group agg-id
|
Required
|
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You can remove any service loop group except those
that are currently referenced by modules.
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For a service loop group containing only one
port, the only way to remove the port from it is to remove the service loop group.
2.1.5 Entering Aggregation Port Group View
In aggregation port group view, you can make
configuration for all the member ports in a link aggregation group at one time.
Follow these steps to enter aggregation
port group view:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
––
|
|
Enter aggregation port group view
|
port-group aggregation agg-id
|
––
|
Caution:
In aggregation port
group view, you can configure aggregation related settings such as STP, VLAN,
QoS, GVRP, Q-in-Q, BPDU tunnel, MAC address learning, but cannot add or remove
member ports.
2.2 Displaying and Maintaining Link Aggregation
|
To do…
|
Use the command…
|
Remarks
|
|
Display the local system ID
|
display lacp system-id
|
Available in any view
|
|
Display detailed information about link
aggregation for the specified port or ports
|
display link-aggregation interface interface-type interface-number [ to
interface-type interface-number ]
|
Available in any view
|
|
Display information about the specified
or all service loop groups
|
display link-aggregation service-type [ agg-id ]
|
Available in any view
|
|
Display summaries for all link
aggregation groups
|
display link-aggregation summary
|
Available in any view
|
|
Display detailed information about
specified or all link aggregation groups
|
display link-aggregation verbose [ agg-id ]
|
Available in any view
|
|
Clear the statistics about LACP for
specified or all ports
|
reset lacp statistics [ interface interface-type interface-number [ to
interface-type interface-number ] ]
|
Available in user view
|
2.3 Link Aggregation Configuration Example
I. Network requirements
l
Switch A aggregates ports GigabitEthernet 1/0/1
through GigabitEthernet 1/0/3 to form one link connected to Switch B and
performs load sharing among these ports.
l
Create a tunnel service-loop group and add port GigabitEthernet
1/0/1 to the group.
II. Network diagram
Figure 2-1 Network
diagram for link aggregation configuration
III. Configuration procedure
This example only
describes how to configure link aggregation on Switch A. To achieve link
aggregation, do the same on Switch B.
1)
In manual aggregation approach
# Create manual aggregation group 1.
<SwitchA> system-view
[SwitchA] link-aggregation group 1
mode manual
# Add ports GigabitEthernet 1/0/1 through GigabitEthernet
1/0/3 to the group.
[SwitchA] interface GigabitEthernet 1/0/1
[SwitchA-GigabitEthernet1/0/1] port
link-aggregation group 1
[SwitchA-GigabitEthernet1/0/1]
interface GigabitEthernet 1/0/2
[SwitchA-GigabitEthernet1/0/2] port
link-aggregation group 1
[SwitchA-GigabitEthernet1/0/2]
interface GigabitEthernet 1/0/3
[SwitchA-GigabitEthernet1/0/3] port
link-aggregation group 1
2)
In static aggregation approach
# Create static aggregation group 1.
<SwitchA> system-view
[SwitchA] link-aggregation group 1
mode static
# Add ports GigabitEthernet 1/0/1 through GigabitEthernet
1/0/3 to the group.
[SwitchA] interface GigabitEthernet 1/0/1
[SwitchA-GigabitEthernet1/0/1] port
link-aggregation group 1
[SwitchA-GigabitEthernet1/0/1]
interface GigabitEthernet 1/0/2
[SwitchA-GigabitEthernet1/0/2] port
link-aggregation group 1
[SwitchA-GigabitEthernet1/0/2]
interface GigabitEthernet 1/0/3
[SwitchA-GigabitEthernet1/0/3] port
link-aggregation group 1
3)
Configure a service loop group
# Create a manual aggregation group.
<SwitchA> system-view
[SwitchA] link-aggregation group 1
mode manual
# Specify this group to be a tunnel service
loop group.
[SwitchA] link-aggregation group 1
service-type tunnel
# Assign port GigabitEthernet 1/0/1 to the
service loop group.
[SwitchA] interface GigabitEthernet 1/0/1
[SwitchA-GigabitEthernet1/0/1] undo
stp
[SwitchA-GigabitEthernet1/0/1] port
link-aggregation group 1
