The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
This chapter describes how to configure EtherChannel on Layer 2 and Layer 3 ports and Link-state Tracking on the Cisco Industrial Ethernet 2000U Series (IE 2000U) and Connected Grid Switches, hereafter referred to as switch.
This chapter includes the following sections:
This section includes the following topics:
An EtherChannel consists of individual Fast Ethernet or Gigabit Ethernet links bundled into a single logical link as shown in Figure 3-1.
Etherchannels provide fault-tolerant high-speed links between switches, routers, and servers.
You can use an EtherChannel to increase the bandwidth between points within the network; and, to address bottlenecks within the network.
EtherChannels provide automatic recovery for the loss of a link by redistributing the load across the remaining links. If a link fails, then the EtherChannel redirects traffic from the failed link to the remaining links in the channel without intervention.
Figure 3-1 Typical EtherChannel Deployment
EtherChannel provides full-duplex bandwidth of up to 800 Mbps between your switch and another switch or host for Fast EtherChannel on a switch with 24 Fast Ethernet ports. For Gigabit EtherChannel, you can configure up to 8 Gbps (8 ports of 1 Gbps), depending on the number of supported Gigabit Ethernet interfaces.
Each EtherChannel can consist of up to eight compatibly configured Ethernet ports. All ports in each EtherChannel must be configured as either Layer 2 or Layer 3 ports. The number of EtherChannels is limited to 48. For more information, see the “Guidelines and Limitations” section. The EtherChannel Layer 3 ports are made up of routed ports. Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface configuration command.
You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), or On mode. PAgP and LACP are available only on NNIs and ENIs. Configure both ends of the EtherChannel in the same mode:
The local port is put into an independent state and continues to carry data traffic as would any other single link. The port configuration does not change, but the port does not participate in the EtherChannel.
If a link within an EtherChannel fails, traffic previously carried over that failed link changes to the remaining links within the EtherChannel. A trap is sent for a failure, identifying the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast packets on one link in an EtherChannel are blocked from returning on any other link of the EtherChannel.
When you create an EtherChannel, a port-channel logical interface is involved.
You also can use the interface port-channel port-channel-number global configuration command to manually create the port-channel logical interface, but then you must use the channel-group channel-group-number command to bind the logical interface to a physical port. The channel-group-number can be the same as the port - channel-number, or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.
For both Layer 2 and Layer 3 ports, the channel-group command binds the physical port and the logical interface together as shown in Figure 3-2.
Each EtherChannel has a port-channel logical interface numbered from 1 to 48. This port-channel interface number corresponds to the one specified with the channel-group interface configuration command.
Figure 3-2 Relationship of Physical Ports, Logical Port Channels, and Channel Groups
After you configure an EtherChannel, configuration changes applied to the port-channel interface apply to all the physical ports assigned to the port-channel interface. Configuration changes applied to the physical port affect only the port to which you apply the configuration. To change the parameters of all ports in an EtherChannel, apply the configuration commands to the port-channel interface.
The Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that can be run only on Cisco switches and on those switches licensed by vendors to support PAgP. PAgP facilitates the automatic creation of EtherChannels by exchanging PAgP packets between Ethernet ports.
NotePAgP is only available on network node interfaces (NNIs) and enhanced network interfaces (ENIs).
By using PAgP, the switch learns the identity of partners capable of supporting PAgP and the capabilities of each port. It 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. For example, PAgP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single switch port.
Table 3-1 shows the user-configurable EtherChannel PAgP modes for the channel-group interface configuration command on an NNI or ENI.
Switch ports exchange PAgP packets only with partner ports configured in the auto or desirable modes. Ports configured in the on mode do not exchange PAgP packets.
Both the auto and desirable modes enable ports to negotiate with partner ports to form an EtherChannel based on criteria such as port speed and, for Layer 2 EtherChannels, trunking state and VLAN numbers.
Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:
A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.
If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.
Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.
Configures your switch as a PAgP physical-port learner and adjusts the priority so that the same port in the bundle is selected for sending packets.
Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a physical learner if it learns addresses by physical ports and directs transmissions based on that knowledge. A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports. The learn method must be configured the same at both ends of the link.
NotePAgP is available only on NNIs and ENIs.
When a device and its partner are both aggregate-port learners, they learn the address on the logical port-channel. The device sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives.
PAgP cannot automatically detect when the partner device is a physical learner and when the local device is an aggregate-port learner. Therefore, you must manually set the learning method on the local device to learn addresses by physical ports. You also must set the load-distribution method to source-based distribution, so that any given source MAC address is always sent on the same physical port.
You also can configure a single port within the group for all transmissions and use other ports for hot standby. The unused ports in the group can be swapped into operation in just a few seconds if the selected single port loses hardware-signal detection. You can configure which port is always selected for packet transmission by changing its priority with the pagp port-priority interface configuration command. The higher the priority, the more likely that the port will be selected.
NoteThe switch supports address learning only on aggregate ports even though thephysical-port keyword is provided in the CLI. The pagp learn-method command and the pagp port-priority command have no effect on the switch hardware, but they are required for PAgP interoperability with devices that only support address learning by physical ports.
When the link partner to the switch is a physical learner, we recommend that you configure the switch as a physical-port learner by using the pagp learn-method physical-port interface configuration command. Set the load-distribution method based on the source MAC address by using the port-channel load-balance src-mac global configuration command. The switch then sends packets to the physical learner switch using the same port in the EtherChannel from which it learned the source address Use the pagp learn-method command only in this situation.
Cisco Discovery Protocol (CDP) sends and receives packets over the physical ports in the EtherChannel.
Note PAgP and CDP are only available on NNIs and ENIs. User network interfaces (UNIs) do not support PAgP or CDP.
Trunk ports send and receive PAgP protocol data units (PDUs) on the lowest numbered VLAN.
In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address to the EtherChannel.
PAgP sends and receives PAgP PDUs only from ports that are up and have PAgP enabled for the auto or desirable mode.
The LACP is defined in IEEE 802.3ad standard and enables Cisco switches to manage Ethernet channels between switches that conform to the standard. LACP facilitates the automatic creation of EtherChannels by exchanging LACP packets between Ethernet ports.
NoteLACP is available only on NNIs and ENIs.
By using LACP, the switch learns the identity of partners capable of supporting LACP and the capabilities of each port. It then dynamically groups similarly configured port s into a single logical link (channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, LACP adds the group to the spanning tree as a single switch port.
Table 3-2 shows the user-configurable EtherChannel LACP modes for the channel-group interface configuration command on an NNI or ENI.
Both the active and passive LACP modes enable ports to negotiate with partner ports to an EtherChannel based on criteria such as port speed and, for Layer 2 EtherChannels, trunking state and VLAN numbers.
Ports can form an EtherChannel when they are in different LACP modes as long as the modes are compatible. For example:
The CDP sends and receives packets over the physical ports in the EtherChannel. Trunk ports send and receive LACP PDUs on the lowest numbered VLAN.
In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address to the EtherChannel.
LACP sends and receives LACP PDUs only from ports that are up and have LACP enabled for the active or passive mode.
EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port to join an EtherChannel without negotiations. It can be useful if the remote device does not support PAgP or LACP. With the on mode, a usable EtherChannel exists only when both ends of the link are configured in the on mode.
NoteFor UNIs, the only available mode is on.
Ports that are configured in the on mode in the same channel group must have compatible port characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they are configured in the on mode.
EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel. EtherChannel load balancing can use MAC addresses or IP addresses, source or destination addresses, or both source and destination addresses. The selected mode applies to all EtherChannels configured on the switch. You configure the load balancing and forwarding method by using the port-channel load-balance global configuration command.
With source-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide load balancing, packets from different hosts use different ports in the channel, but packets from the same host use the same port in the channel.
With destination-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the destination-host MAC address of the incoming packet. Therefore, packets to the same destination are forwarded over the same port, and packets to a different destination are sent on a different port in the channel.
With source-and-destination MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on both the source and destination MAC addresses. This forwarding method, a combination source-MAC and destination-MAC address forwarding methods of load distribution, can be used if it is not clear whether source-MAC or destination-MAC address forwarding is better suited on a particular switch. With source-and-destination MAC-address forwarding, packets sent from host A to host B, host A to host C, and host C to host B could all use different ports in the channel.
With source-IP-address-based forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the EtherChannel based on the source-IP address of the incoming packet. Therefore, to provide load-balancing, packets from different IP addresses use different ports in the channel, but packets from the same IP address use the same port in the channel.
With destination-IP-address-based forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the EtherChannel based on the destination-IP address of the incoming packet. Therefore, to provide load-balancing, packets from the same IP source address sent to different IP destination addresses could be sent on different ports in the channel. But packets sent from different source IP addresses to the same destination IP address are always sent on the same port in the channel.
With source-and-destination IP address-based forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the EtherChannel based on both the source and destination IP addresses of the incoming packet. This forwarding method, a combination of source-IP and destination-IP address-based forwarding, can be used if it is not clear whether source-IP or destination-IP address-based forwarding is better suited on a particular switch. In this method, packets sent from the IP address A to IP address B, from IP address A to IP address C, and from IP address C to IP address B could all use different ports in the channel.
Different load-balancing methods have different advantages, and the choice of a particular load-balancing method should be based on the position of the switch in the network and the kind of traffic that needs to be load-distributed. In Figure 3-3, an EtherChannel of four workstations communicates with a router. Because the router is a single-MAC-address device, source-based forwarding on the switch EtherChannel ensures that the switch uses all available bandwidth to the router. The router is configured for destination-based forwarding because the large number of workstations ensures that the traffic is evenly distributed from the router EtherChannel.
Use the option that provides the greatest variety in your configuration. For example, if the traffic on a channel is going only to a single MAC address, using the destination-MAC address always chooses the same link in the channel. Using source addresses or IP addresses might result in better load balancing.
Figure 3-3 Load Distribution and Forwarding Methods
Ensure that you have all the required information to configure EtherChannels in your network.
Ensure that you have all the required information to configure Link-state Tracking in your network.
– Do not try to configure more than 48 EtherChannels on the switch.
– Configure a PAgP EtherChannel including only NNIs or only ENIs.
– Configure a LACP EtherChannel including only NNIs or only ENIs.
– When you disable a port within an EtherChannel by using the shutdown interface configuration, the software interprets this as a link failure. As a result, the software transfers the traffic for that disabled port to one of the remaining ports in the EtherChannel.
– UNIs and ENIs are disabled by default. NNIs are enabled by default.
– Spanning-tree path cost for each VLAN
– Spanning-tree port priority for each VLAN
– Spanning-tree Port Fast setting
Note Spanning Tree Protocol is only supported on NNIs or ENIs on which it has been specifically enabled.
Note PAgP and LACP are only available on NNIs and ENIs.
Layer 2 and Layer 3 EtherChannels
– Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.
– If you configure an EtherChannel from trunk ports, verify that the trunking mode is the same on all the trunks. Inconsistent trunk modes on EtherChannel ports can have unexpected results.
– An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.
– NNIs or ENIs with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.
– System ID (a combination of the LACP system priority and the switch MAC address)
|
|
---|---|
NoteAfter you configure an EtherChannel, configuration changes applied to the port-channel interface apply to all the physical ports assigned to the port-channel interface, and configuration changes applied to the physical port affect only the port to which you apply the configuration.
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
|
|
|
---|---|---|
Specify a physical port, and enter interface configuration mode. Valid interfaces include physical ports. For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group. For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode. Note If the interface is a UNI, you must enter the port-type {eni | nni} interface configuration command before configuring PAgP or LACP. |
||
Enable the port, if necessary. By default, UNIs and ENIs are disabled, and NNIs are enabled. |
||
Assign all ports as static-access ports in the same VLAN, or configure them as trunks. If you configure the port as a static-access port, assign it to only one VLAN. The range is 1 to 4094. |
||
channel-group channel -group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive } |
Assign the port to a channel group, and specify the PAgP or the LACP mode. For channel-group-number , the range is 1 to 48. Note For UNIs, the only available mode is on. For mode , select one of these keywords:
To remove a port from the EtherChannel group, use the no channel-group interface configuration command. Note For information on compatible modes for the switch and its partner, see the “PAgP Modes” section and the “LACP Modes” section. To remove a port from the EtherChannel group, use the no channel-group interface configuration command. |
|
To remove a port from the EtherChannel group, use the no channel-group interface configuration command.
This example shows how to configure an EtherChannel. It assigns two ports as static-access ports in VLAN 10 to channel 5 with the PAgP mode desirable :
This example shows how to configure an EtherChannel. It assigns two ports as static-access ports in VLAN 10 to channel 5 with the LACP mode active :
To configure Layer 3 EtherChannels, you create the port-channel logical interface and then put the Ethernet ports into the port-channel as described in the next two sections.
When configuring Layer 3 EtherChannels, you should first manually create the port-channel logical interface by using the interface port-channel global configuration command. Then you put the logical interface into the channel group by using the channel-group interface configuration command.
NoteTo move an IP address from a physical port to an EtherChannel, you must delete the IP address from the physical port before configuring it on the port-channel interface.
Beginning in privileged EXEC mode, follow these steps to create a port-channel interface for a Layer 3 EtherChannel. This procedure is required.
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
|
|
|
---|---|---|
Specify the port-channel logical interface, and enter interface configuration mode. For port - channel-number, the range is 1 to 48. Note To remove the port-channel, use the no interface port-channel port-channel-number global configuration command. |
||
Assign an Ethernet port to the Layer 3 EtherChannel. For more information. See Defining the Physical Interfaces. |
This example shows how to create the logical port channel 5 and assign 172.10.20.10 as its IP address:
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
|
|
|
---|---|---|
Specify a physical port, and enter interface configuration mode. Valid interfaces include physical ports. For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group. For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode. Note If the interface is a UNI, you must enter the port-type {eni | nni} interface configuration command before configuring PAgP or LACP. |
||
Enable the port, if necessary. By default, UNIs and ENIs are disabled, and NNIs are enabled. |
||
Ensure that there is no IP address assigned to the physical port. |
||
channel-group channel -group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive } |
Assign the port to a channel group, and specify the PAgP or the LACP mode. For channel-group-number , the range is 1 to 48. This number must be the same as the port-channel-number (logical port) configured in the “Creating Port-Channel Logical Interfaces” section. Note For UNIs, the only available mode is on. For mode , select one of these keywords:
For information on compatible modes for the switch and its partner, see the “PAgP Modes” section and the “LACP Modes” section. |
|
This example shows how to configure an EtherChannel. It assigns two ports to channel 5 with the LACP mode active :
This section describes how to configure EtherChannel load balancing by using source-based or destination-based forwarding methods. For more information, see the “Load Balancing and Forwarding Methods” section.
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
This section describes how to configure EtherChannel load balancing by using the source-MAC address of the incoming packet as the basis for distribution.
Configures your switch as a PAgP physical-port learner and adjusts the priority so that the same port in the bundle is selected for sending packets.
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
Configure EtherChannel Load Balancing. (See Configuring EtherChannel Load Balancing (Optional).)
|
|
|
---|---|---|
Specify the port for transmission, and enter interface configuration mode. Note If the interface is a UNI, you must enter the port-type {eni | nni} interface configuration command before configuring LACP. |
||
Select the PAgP learning method. By default, aggregation-port learning is selected, which means the switch sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives. Select physical-port to connect with another switch that is a physical learner. Make sure to configure the port-channel load-balance global configuration command to src-mac as described in the “Configuring EtherChannel Load Balancing (Optional)” section. The learning method must be configured the same at both ends of the link. If the interface is a UNI, you must enter the port-type { eni | nni } interface configuration command before configuring PAgP. To return the learning method to its default setting, use the no pagp learn-method interface configuration command. |
||
Assign a priority so that the selected port is chosen for packet transmission. For priority , the range is 0 to 255. The default is 128. The higher the priority, the more likely that the router chooses the port for PAgP transmission. To return the priority to its default setting, use the no pagp port-priority interface configuration command. |
||
This example shows how to configure the switch as a PAgP physical-port learner to adjust the priority so that the router selects the same port in the bundle for sending packets.
When enabled, LACP tries to configure the maximum number of LACP-compatible ports in a channel, up to a maximum of 16 ports. Only eight LACP links can be active at one time. The software places any additional links in a hot-standby mode. If one of the active links becomes inactive, a link that is in the hot-standby mode becomes active in its place.
NoteLACP is only available on NNIs and ENIs.
You can configure the system priority for all of the EtherChannels.
You cannot configure a system priority for each LACP-configured channel. By changing this value from the default, you can affect how the software selects active and standby links.
You can use the show etherchannel summary privileged EXEC command to see which ports are in the hot-standby mode (denoted with an H port-state flag).
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
By default, all ports use the same port priority. If the local system has a lower value for the system priority and the system ID than the remote system, you can affect which of the hot-standby links become active first by changing the port priority of LACP EtherChannel ports to a lower value than the default.
NoteIf LACP is not able to aggregate all the ports that are compatible (for example, the remote system might have more restrictive hardware limitations), all the ports that cannot be actively included in the EtherChannel are put in the hot-standby state and are used only if one of the channeled ports fails.
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
To display EtherChannel, PAgP, and LACP status information, use the privileged EXEC commands described below.
You can clear PAgP channel-group information and traffic counters by using the clear pagp { channel-group-number counters | counters } privileged EXEC command.
You can clear LACP channel-group information and traffic counters by using the clear lacp { channel-group-number counters | counters } privileged EXEC command.
Link-state tracking, also known as trunk failover, is a feature that binds the link state of multiple interfaces. For example, link-state tracking provides redundancy in the network when used with Flex Links. If the link is lost on the primary interface, connectivity is transparently switched to the secondary interface.
As shown in Figure 3-4, Cisco IE 2000U switches are used as user-facing provider edge (UPE) switches in a customer site at the edge of the provider network connected to a customer premises equipment (CPE) switch. The UPE switches are connected to the provider edge (PE) switches in the service provider (SP) network. Customer devices, such as clients, connected to the CPE switch have multiple connections to the SP network. This configuration ensures that the traffic flow is balanced from the customer site to the SP and the reverse. Ports connected to the CPE are referred to as downstream ports, and ports connected to PE switches are referred to as upstream ports.
Figure 3-4 Typical Link-State Tracking Configuration
|
|
---|---|
Review the Guidelines and Limitations for this feature. (See Guidelines and Limitations.)
This example shows how to create a link-state group and configure the interfaces:
Use the show link state group command to display the link-state group information. Enter this command without keywords to display information about all link-state groups. Enter the group number to display information specific to the group. Enter the detail keyword to display detailed information about the group.
This is an example of output from the show link state group 1 command:
This is an example of output from the show link state group detail command:
This example shows how to create a link-state group and configure the interfaces:
|
|
---|---|