Latest Contents. It is our pleasure to officially announce the finalists in the IT Blog Awards. Now we are looking to YOU, our amazing tech community, to weigh in. Check out the amazing educational content we've uncovered and vote for your favorites before Friday, Fe Created by Mohamed Alhenawy on AM. SDN is a centralized approach to network management which abstract OSPF inter-area loop prevention and discard route issues.
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In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode. If you do not specify non-silent , silent is assumed. The silent setting is for connections to file servers or packet analyzers. This setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission. It places the port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.
You can configure EtherChannel load-balancing by using source-based or destination-based forwarding methods. The default is src-mac. 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. Selects 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.
For priority , the range is 0 to The default is The higher the priority, the more likely that the port will be used for PAgP transmission. 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. If you configure more than eight links for an EtherChannel group, the software automatically decides which of the hot-standby ports to make active based on the LACP priority. To every link between systems that operate LACP, the software assigns a unique priority made up of these elements in priority order :.
In priority comparisons, numerically lower values have higher priority. The priority decides which ports should be put in standby mode when there is a hardware limitation that prevents all compatible ports from aggregating.
Determining which ports are active and which are hot standby is a two-step procedure. First the system with a numerically lower system priority and system ID is placed in charge of the decision.
Next, that system decides which ports are active and which are hot standby, based on its values for port priority and port number. The port priority and port number values for the other system are not used. You can configure the system priority for all the EtherChannels that are enabled for LACP by using the lacp system-priority global configuration command.
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.
This procedure is optional. 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.
The hot-standby ports that have lower port numbers become active in the channel first. If 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.
For priority , the range is 1 to The lower the value, the more likely that the port will be used for LACP transmission. Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.
This example shows how to configure an EtherChannel on a single switch in the stack. This example shows how to configure a cross-stack EtherChannel. The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.
Access to most tools on the Cisco Support website requires a Cisco. Skip to content Skip to search Skip to footer. Book Contents Book Contents. Find Matches in This Book. PDF - Complete Book 4. Updated: February 11, Chapter: Configuring EtherChannels. Channel groups.
None assigned. Port-channel logical interface. None defined. PAgP learn method. Aggregate-port learning on all ports.
PAgP priority. LACP learn method. LACP port priority. LACP system priority. Determining which ports are active and which are hot standby is a two-step procedure. First the system with a numerically lower system priority and system-id is placed in charge of the decision. Next, that system decides which ports are active and which are hot standby, based on its values for port priority and port number. The port-priority and port-number values for the other system are not used.
You can configure the system priority for all the EtherChannels that are enabled for LACP by using the lacp system-priority global configuration command. 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.
For priority , the range is 1 to The lower the value, the higher the system priority. To return the LACP system priority to the default value, use the no lacp system-priority global configuration command. 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. The hot-standby ports that have lower port numbers become active in the channel first.
Note If 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.
Specify the port to be configured, and enter interface configuration mode. The lower the value, the more likely that the port will be used for LACP transmission. To return the LACP port priority to the default value, use the no lacp port-priority interface configuration command. Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.
For detailed information about the fields in the displays, see the command reference f or this release. 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 server NIC adapter teaming. When the server network adapters are configured in a primary or secondary relationship known as teaming, if the link is lost on the primary interface, connectivity is transparently changed to the secondary interface.
Note An interface can be an aggregation of ports an EtherChannel , or a single physical port in access or trunk mode. Figure shows a network configured with link-state tracking.
To enable link-state tracking, create a link-state group , and specify the interfaces that are assigned to the link-state group. In a link-state group, these interfaces are bundled together.
The downstream interfaces are bound to the upstream interfaces. Interfaces connected to servers are referred to as downstream interfaces, and interfaces connected to distribution switches and network devices are referred to as upstream interfaces. The configuration in Figure ensures that the network traffic flow is balanced as follows:. Port 1 is connected to server 1, and port 2 is connected to server 2. Port 1 and port 2 are the downstream interfaces in link-state group 1.
Port 5 and port 6 are the upstream interfaces in link-state group 1. Port 3 is connected to server 3, and port 4 is connected to server 4. Port 3 and port 4 are the downstream interfaces in link-state group 2.
Port 7 and port 8 are the upstream interfaces in link-state group 2. Port 5 and port 6 are the upstream interfaces in link-state group 2. Port 7 and port 8 are the upstream interfaces in link-state group 1. In a link-state group, the upstream ports can become unavailable or lose connectivity because the distribution switch or router fails, the cables are disconnected, or the link is lost.
These are the interactions between the downstream and upstream interfaces when link-state tracking is enabled:. As an example of a connectivity change from link-state group 1 to link-state group 2 on switch A, see Figure If the upstream link for port 6 is lost, the link states of downstream ports 1 and 2 do not change. However, if the link for upstream port 5 is also lost, the link state of the downstream ports changes to the link-down state.
Connectivity to server 1 and server 2 is then changed from link-state group1 to link-state group 2. The downstream ports 3 and 4 do not change state because they are in link-group 2.
You can recover a downstream interface link-down condition by removing the failed downstream port from the link-state group. To recover multiple downstream interfaces, disable the link-state group.
There are no link-state groups defined, and link-state tracking is not enabled for any group. Beginning in privileged EXEC mode, follow these steps to configure a link-state group and to assign an interface to a group:. Create a link-state group, and enable link-state tracking. The group number can be 1 to 2; the default is 1. Specify a physical interface or range of interfaces to configure, and enter interface configuration mode. Valid interfaces include switch ports in access or trunk mode IEEE Specify a link-state group, and configure the interface as either an upstream or downstream interface in the group.
This example shows how to create a link-state group and configure the interfaces:. To disable a link-state group, use the no link state track number global configuration command. 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:. For detailed information about the fields in the display, see the command reference for this release. Skip to content Skip to search Skip to footer. Book Contents Book Contents. Find Matches in This Book.
PDF - Complete Book Updated: July 22, Configure both ends of the EtherChannel in the same mode: When you configure one end of an EtherChannel in either PAgP or LACP mode, the system negotiates with the other end of the channel to determine which ports should become active.
Incompatible ports are put into an independent state and continue 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. When you configure an EtherChannel in the on mode, no negotiations take place.
The switch forces all compatible ports to become active in the EtherChannel. The other end of the channel on the other switch must also be configured in the on mode; otherwise, packet loss can occur. You can create the EtherChannel in these ways: Use the channel-group interface configuration command. This command automatically creates the port-channel logical interface when the channel group gets its first physical port.
Use the interface port-channel port-channel-number global configuration command to manually create the port-channel logical interface. Then use the channel-group channel-group-number interface configuration 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. Figure 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.
For example: A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode. Once you assign the interfaces to the port-channel, you will see that the switch creates a new port-channel interface. After configuring the interfaces you will see the following on your console:. This means our port-channel is operational. To verify that both interfaces are working you can use the following command:. Rene, this looks like outstanding work.
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