Making changes to an EtherChannel using Dynamic Adapter Membership

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Making changes using Dynamic Adapter Membership does not require you to stop all traffic going over the EtherChannel by detaching its interface.

Consider the following before proceeding:

  1. When adding an adapter at runtime, note that different Ethernet adapters support different capabilities (for example, the ability to do checksum offload, to use private segments, to do large sends, and so forth). If different types of adapters are used in the same EtherChannel, the capabilities reported to the interface layer are those supported by all of the adapters (for example, if all but one adapter supports the use of private segments, the EtherChannel will state it does not support private segments; if all adapters do support large send, the channel will state it supports large send). When adding an adapter to an EtherChannel at runtime, be sure that it supports at least the same capabilities as the other adapters already in the EtherChannel. If you attempt to add an adapter that does not support all of the capabilities the EtherChannel supports, the addition will fail. Note, however, that if the EtherChannel's interface is detached, you may add any adapter (regardless of the capabilities it supports), and when the interface is reactivated the EtherChannel will recalculate the capabilities it supports based on the new list of adapters.
  2. If you are not using an alternate address and you plan to delete the adapter whose MAC address was used for the EtherChannel (the MAC address used for the EtherChannel is "owned" by one of the adapters), the EtherChannel will use the MAC address of the next adapter available. In other words, the one that becomes the first adapter after the deletion, or the backup adapter in case all main adapters are deleted. For example, if an EtherChannel has main adapters ent0 and ent1 and backup adapter ent2, it uses by default ent0's MAC address (it is then said that ent0 "owns" the MAC address). If ent0 is deleted, the EtherChannel then uses ent1's MAC address. If ent1 is then deleted, the EtherChannel uses ent2's MAC address. If ent0 is later re-added to the EtherChannel, it continues to use ent2's MAC address because ent2 is now the owner of the MAC address. If ent2 were then deleted from the EtherChannel, it starts using ent0's MAC address again.

    Deleting the adapter whose MAC address was used for the EtherChannel may cause a temporary loss of connectivity, because all of the adapters in the EtherChannel need to be reset so they learn of their new hardware address. Some adapters take a few seconds to be initialized.

    If your EtherChannel is using an alternate address (a MAC address you specified), it keeps using this MAC address regardless of which adapters are added or deleted. Furthermore, it means that there is no temporary loss of connectivity when adding or deleting adapters because none of the adapters "owns" the EtherChannel's MAC address.

  3. Almost all EtherChannel attributes can now be modified at runtime. The only exception is Enable Gigabit Ethernet Jumbo Frames. To modify the Enable Gigabit Ethernet Jumbo Frames attribute, you must first detach the EtherChannel's interface before attempting to modify this value.
  4. For any attribute that cannot be changed at runtime (currently, only Enable Gigabit Ethernet Jumbo Frames), there is a field called Apply change to DATABASE only. If this attribute is set to yes, it is possible to change, at runtime, the value of an attribute that usually cannot be modified at runtime. With the Apply change to DATABASE only field set to yes the attribute will only be changed in the ODM and will not be reflected in the running EtherChannel until it is reloaded into memory (by detaching its interface, using rmdev -l EtherChannel_device and then mkdev -l EtherChannel_device commands), or until the machine is rebooted. This is a convenient way of making sure that the attribute is modified the next time the machine boots, without having to disrupt the running EtherChannel.
  5. In a logical partition, when you remove an adapter from an EtherChannel, you must also remove the associated switch port from the EtherChannel in the switch. Otherwise, the connectivity might be lost because the switch might be using the same switch port for communication.

To make changes to the EtherChannel or Link Aggregation using Dynamic Adapter Membership, follow these steps:

  1. At the command line, type smitty etherchannel.
  2. Select Change / Show Characteristics of an EtherChannel / Link Aggregation.
  3. Select the EtherChannel or Link Aggregation that you want to modify.
  4. Fill in the required fields according to the following guidelines:
    • In the Add adapter or Remove adapter field, select the Ethernet adapter you want to add or remove.
    • In the Add backup adapter or Remove backup adapter fields, select the Ethernet adapter you want to start or stop using as a backup.
    • Almost all of the EtherChannel attributes can be modified at runtime, although the Enable Gigabit Ethernet Jumbo Frames attribute cannot.
    • To turn a regular EtherChannel into an IEEE 802.3ad Link Aggregation, change the Mode attribute to 8023ad. To turn an IEEE 802.3ad Link Aggregation into an EtherChannel, change the Mode attribute to standard or round_robin.
  5. Fill in the necessary data, and press Enter.