Information About Link Aggregation Group
A link aggregation group (LAG) bundles all of the controller’s distribution system ports into a single 802.3ad port channel. This reduces the number of IP addresses required to configure the ports on your controller. When LAG is enabled, the system dynamically manages port redundancy and load balances access points transparently to the corresponding user.
LAG simplifies controller configuration because you no longer have to configure ports for each interface. If any of the controller ports fail, traffic is automatically migrated to one of the other ports. As long as at least one controller port is functioning, the system continues to operate, access points remain connected to the network, and wireless clients continue to send and receive data.
Note |
The wireless management VLAN can only be part of one port channel. |
Note |
LACP is supported on a standalone controller from Cisco IOS XE Gibraltar 16.12.x release. LACP is supported on an SSO pair from Cisco IOS XE Amsterdam 17.1.1s onwards. |
Link Aggregation Control Protocol
Link Aggregation Control Protocol (LACP) is a part of an IEEE specification (802.3ad) that allows you to bundle several physical ports together to form a single logical channel. LACP allows a switch to negotiate an automatic bundle by sending LACP packets to a peer. By using the LACP, the wireless controller learns the identity of peers that are capable of supporting LACP, and the capabilities of each port. The LACP then dynamically groups similarly configured ports into a single logical link (channel or aggregate port). Similarly, configured ports are grouped based on hardware, administrative, and port parameter constraints. If any of the controller ports fail, traffic is automatically migrated to one of the other ports. As long as at least one controller port is functioning, the system continues to operate, access points remain connected to the network, and wireless clients continue to send and receive data.
Configuring LAG Using LACP
To configure LAG using LACP, multiple port-channel interfaces must be created, and these interfaces should be added to the corresponding port bundle. LACP should also be configured on the uplink switch for the LACP bundle to come up.
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Create a port-channel interface
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Add interface to the port-channel
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Add VLAN to LAG
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Add interface to the port-channel
Port Aggregation Protocol
Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that you can run on controllers. PAgP facilitates the automatic creation of EtherChannels by exchanging PAgP packets between Ethernet ports. PAgP packets are sent between Fast EtherChannel-capable ports in order to form a channel. When any of the active ports fail, a standby port becomes active.
By using PAgP, the controller learns the identity of partners that are capable of supporting PAgP and the capabilities of each port. PAgP then dynamically groups similarly configured ports (on a single device in a stack) into a single logical link (channel or aggregate port). Similarly, configured ports are grouped based on hardware, administrative, and port parameter constraints.
Configuring LAG Using PAgP
To configure LAG using PAgP, multiple port-channel interfaces must be created, and these interfaces should be added to the corresponding port bundle. PAgP should also be configured on the uplink switch for the PAgP bundle to come up.
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Create a port-channel interface
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Add interface to the port-channel
Information about Flow Control
Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing congested nodes to pause link operation at the other end. If one port experiences congestion and cannot receive more traffic, it notifies the other port by sending a pause frame to stop sending until the condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets, preventing any data packet loss during the congestion period.
Flow control is enabled by default for both bay0 and bay1 ports as a day-1 behavior. We suggest turning on flow control on uplink switch if overruns are seen on a Cisco Catalyst 9800-L Wireless Controller due to burst traffic. This will help uplink switch to honor flow control settings enabled on the controller.
Note |
Though the show command might show the status as flow control off or unsupported on the controller's CLI, the actual & default behavior is turned on. For more information, check https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwk52366. |
Configuring LAG in ON Mode
To configure LAG in ON mode, multiple port-channel interfaces must be created, and these interfaces should be added to the corresponding port bundle. LACP should also be configured on the uplink switch for the LACP bundle to come up.
Multichassis Link Aggregation Group
From Cisco IOS XE Amsterdam 17.2.1, Multichassis Link Aggregation Group (multi-LAG), which provides flexibility in connecting the controller to a switch's infrastructure is supported. Using multi-LAG, you can connect the multiple uplinks from the controller to the separated uplink switches. The controller supports VLAN-based traffic splitting when connected to a multiswitch topology. This provides the ability to distribute traffic on different uplinks, based on VLANs, for example, supporting a use case where guest traffic can be completely isolated to a different switch or network from the enterprise network. Same VLAN cannot be configured on both the uplinks.
You can connect a LAG to a single switch. However, different VLANs must be connected to different LAGs. The redundancy port must be connected to the same distribution switch as the uplinks, or back to back.
Multi-LAG is supported in LAG ON mode, LACP, and PAgP modes.
Prerequisites for Multi-LAG
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Each LAG must be connected to a single switch.
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Different VLANs must be assigned to different LAGs.
Restrictions for Multi-LAG
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If the primary LAG fails, automatic failover to secondary LAG is not supported.
Supported Topologies
The Cisco Catalyst 9800-80 Wireless Controller has eight ports, while the Cisco Catalyst 9800-40 and Cisco Catalyst 9800-L wireless controllers have four ports each. You can create multi-LAGs of ports with similar capabilities, for example, 2.5 G and 2.5 G, or 10 G and 10 G. You cannot have a 2.5 G and a 10 G port in a port channel group with a minimum of two ports in one LAG.
Configuring a Port Channel Interface (GUI)
Procedure
Step 1 |
Choose Configuration > Interface > Logical. |
Step 2 |
Click the Port Channel tab to configure the Port Channel interface. The Port Channel tab lists all the logical port-channel interfaces on the device. |
Step 3 |
Click Add to add to a new logical port channel interface. The Add Port Channel Interface window is displayed. |
Step 4 |
In the Add Port Channel Interface complete the following procedure: |
Create a Port-Channel Interface
Follow the procedure given below to create a port-channel interface.
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface port-channel port-channel Example:
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Configures the port channel and enters interface configuration mode. The valid values for the port channel number ranges from 1 to 64. |
Step 3 |
switchport mode trunk Example:
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Configures the port as trunk. |
Step 4 |
no shutdown Example:
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Enables the interface. |
Configuring LAG in ON Mode
Follow the procedure given below to configure LAG in ON mode.
Procedure
Command or Action | Purpose | |
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Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface TenGigabitEthernet port-slot Example:
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Configures the port. |
Step 3 |
switchport mode trunk Example:
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Configures the port as trunk. |
Step 4 |
no shutdown Example:
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Disables the interface. |
Step 5 |
channel-group group-number mode on Example:
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Assigns the port to a channel group, and specifies the ON mode. The valid values for the port channel number ranges from 1 to 64. |
Step 6 |
switchport trunk allowed vlan vlan-id Example:
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Assigns the allowed VLAN ID to the port when it is in trunking mode. |
Add an Interface to a Port Channel (LACP)
Follow the procedure given below to add an interface to a port channel using the LACP.
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface TenGigabitEthernet port-slot Example:
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Configures the port. |
Step 3 |
channel-group group-number {active | passive} Example:
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Assigns the port to a channel group, and specifies the LACP mode. The valid values for the port channel number ranges from 1 to 64. |
Step 4 |
switchport mode trunk Example:
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Configures the port as trunk. |
Add an Interface to a Port Channel (PAgP)
Follow the procedure given below to add an interface to a port channel using the PAgP.
Procedure
Command or Action | Purpose | |
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Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface TenGigabitEthernet port-slot Example:
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Configures the TenGigabit Ethernet interface. |
Step 3 |
channel-group group-number {auto | desirable} Example:
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Assigns the port to a channel group, and specifies the PAgP mode. The valid values for the port channel number ranges from 1 to 64. |
Step 4 |
switchport mode trunk Example:
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Configures the port as trunk. |
Add a VLAN to a Port Channel
Follow the procedure given below to add different VLANs under a port channel.
Procedure
Command or Action | Purpose | |
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Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface port-channel port-channel Example:
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Configures the port channel. Valid values for the port channel number range from 1 to 64. |
Step 3 |
switchport trunk allowed vlan vlan-id Example:
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Adds VLANs to the list of allowed VLANs. |
Remove a Port Channel Group from a Physical Interface
Perform this task to remove a port channel group from a physical port.
Procedure
Command or Action | Purpose | |
---|---|---|
Step 1 |
configure terminal Example:
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Enters global configuration mode. |
Step 2 |
interface TenGigabitEthernet port-slot Example:
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Enters the TenGigabit Ethernet interface. |
Step 3 |
no channel-group Example:
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Removes the port channel group from the physical port. |
Step 4 |
end Example:
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Exits interface configuration mode. |
Verify the LAG Configuration
To view a port channel's state, use the following command:
Device# show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator
M - not in use, minimum links not met
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
A - formed by Auto LAG
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
3 Po3(SU) LACP Tw0/0/0(P) Tw0/0/1(P)
4 Po4(SU) LACP Tw0/0/2(P) Tw0/0/3(P)
To verify an LACP or PAgP configuration, use the following commands:
Device# show running-config interface tenGigabitEthernet 0/0/0
Building configuration...
Current configuration : 114 bytes
!
interface TwoGigabitEthernet0/0/0
switchport trunk allowed vlan 16,17
switchport mode trunk
speed 1000
no negotiation auto
no snmp trap link-status
channel-group 3 mode on
Device# show running-config interface port-channel 1
Building configuration...
Current configuration : 54 bytes
!
interface Port-channel1
switchport mode trunk
switchport trunk allowed vlan 10,30,50
end