Technotes (FAQs)

Draft : Determining type of Etherchannel adapter

Question

How do I determine what type of Etherchannel adapter I'm using or have setup on my AIX machine?

In AIX, there are basically three types of Etherchannel adapters that can be configured. They are standard (Cisco) Etherchannel, 802.3ad/LACP, Link Aggregation Control Protocol, and NIB, or Network Interface Backup. The different schemes are accomplished by different combinations of the 'mode' attribute and the number of adapters in the primary channel ('adapter_names' attribute) and the backup adapter ('backup_adapter' attribute). The round_robin mode is actually a form of load balancing and in reality, is rarely used.

The best way to determine the actual type of Etherchannel is to use a few basic commands from the AIX command line and this document as a guide.

First, to list all the Etherchannel adapters on the machine run this command:

lsdev -Cc adapter | grep -i chan

example output:

scooterbso:/ lsdev -Cc adapter | grep -i chan

ent8 Available EtherChannel / IEEE 802.3ad Link Aggregation

Second, list the characteristics of the Etherchannel by running an lsattr -El entX,
where X is the number of your Etherchannel adapter as determined in the first step above.

example:

scooterbso:/ lsattr -El ent8

adapter_names ent2,ent3 EtherChannel Adapters True
alt_addr 0x000000000000 Alternate EtherChannel Address True
auto_recovery yes Enable automatic recovery after failover True
backup_adapter NONE Adapter used when whole channel fails True
hash_mode default Determines how outgoing adapter is chosen True
interval long Determines interval value for IEEE 802.3ad mode True
mode standard EtherChannel mode of operation True
netaddr 0 Address to ping True
noloss_failover yes Enable lossless failover after ping failure True
num_retries 3 Times to retry ping before failing True
retry_time 1 Wait time (in seconds) between pings True
use_alt_addr no Enable Alternate EtherChannel Address True
use_jumbo_frame no Enable Gigabit Ethernet Jumbo Frames True

The output of lsattr -El entX shows the settings of a device that are stored in the ODM. The output of the entstat -d entX command will show the settings of the Etherchannel adapter in the 'running system'. The two are usually the same, but could be different if the changes were applied to the ODM, but have not been incorporated into the 'running system'

Rules:

1.) If there are one or more adapters showing in the 'adapter_names' field, AND the 'mode' is 'standard', this is configured as an 'aggregate' and is considered to be standard Cisco Etherchannel. It requires that all the connections go to the same network switch and they all be 'trunked' together into an aggregate. If you run an entstat -d entX, where entX is the number for the Etherchannel adapter, it will eventually show you this section in the output. This is how a 'standard' mode (Cisco) Etherchannel will show up.

(partial output from entstat -d on Etherchannel adapter)

===========================================
Statistics for every adapter in the EtherChannel:
-------------------------------------------------

Number of adapters: 2
Operating mode: Standard mode
Hash mode: Destination IP address
===========================================

2.) If there is one or more adapters showing in the 'adapter_names' field, AND the 'mode' is set to '802.3ad', this is configured as an 'aggregate' as well, but is considered to be LACP (Link Aggregation Control Protocol). It also requires all connections go to the same switch and it be configured for LACP. If you run an entstat -d entX, where entX is the number for the Etherchannel adapter, it will eventually show you this section of the output. This is how an 802.3ad or an LACP mode Etherchannel will show up.

(partial output from entstat -d on Etherchannel adapter)

===================================================
Statistics for every adapter in the IEEE 802.3ad Link Aggregation:
------------------------------------------------------------------

Number of adapters: 2
Operating mode: Standard mode (IEEE 802.3ad)
IEEE 802.3ad Link Aggregation Statistics:
...
Hash mode: Destination IP address
===================================================

3.) If there is only one adapter in the 'adapter_names' field, AND no 'backup' adapter, then the 'mode' still determines what type of etherchannel it will be, either standard Cisco Etherchannel or LACP. I have seen cases where the Customer has it configured as such and all seems to work well with just one adapter, although it is not very useful, since you have neither the additional bandwidth nor the redundancy of multiple adapters.

Refer to this link for further information on both modes.

Etherchannel and IEEE 802.3ad Link Aggregation

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.commadmn/doc/commadmndita/etherchannel_intro.htm

4.) If there is only one adapter in the 'adapter_names' field AND you have also specified a 'backup' adapter, then this is the third type of Etherchannel adapter you can have, and it is referred to as NIB, or Network Interface Backup mode. This is also referred to as an 'Active/Passive' type setup. This configuration does NOT require any special setup on the switch ports, although for higher reliability, both connections should go to a different network switch. If you run an entstat -d entX, where entX is the number for the Etherchannel adapter, it will eventually show you this section of the output. This is how an NIB, or Network Interface Backup mode Etherchannel will show up.

(partial output from entstat -d on Etherchannel adapter)

===========================================
Statistics for every adapter in the EtherChannel:
-------------------------------------------------

Number of adapters: 2
Active channel: primary channel
Operating mode: Network interface backup mode
===========================================

Refer to this link for further information:

Network Interface Backup Configuration

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.commadmn/doc/commadmndita/etherchannel_backupconfig.htm

5.) If you have two or more adapters showing up in the 'adapter_names' field AND you also have a single 'backup' adapter, then again, the 'mode' of the etherchannel determines if this is going to be standard (Cisco) Etherchannel or 802.3ad/LACP.
This will not configure nor show up as an NIB type Etherchannel. If you run an entstat -d entX, where entX is the number for the Etherchannel adapter, it will eventually show you this section of the output.

(partial output from entstat -d on Etherchannel adapter)

===========================================
Statistics for every adapter in the EtherChannel:
-------------------------------------------------

Number of adapters: 3
Active channel: primary channel
Operating mode: Standard mode
Hash mode: Destination IP address
===========================================

And if you have two or more adapters showing up in the 'adapter_names' field AND one 'backup' adapter, but have the mode set to 802.3ad, this is what the entstat output will show in the Statistics section.

(partial output from entstat -d on Etherchannel adapter)

===================================================
Statistics for every adapter in the IEEE 802.3ad Link Aggregation:
------------------------------------------------------------------

Number of adapters: 3
Active channel: primary channel
Operating mode: Standard mode (IEEE 802.3ad)
===================================================

6.)With Dynamic Adapter Membership, you can Add/Delete adapters from an Etherchannel dynamically, and even change the mode from smitty etherchannel. One caution regarding this however. You can change from one mode to the other and break the etherchannel perhaps, depending on which way you go and how the network switch is setup. Therefore, despite the fact that you can add or delete adapters dynamically, or 'on-the-fly', you should avoid doing so without your Network Administrators at least on standby to assist you in changing the switch configuration if need be.

Refer to keyword 'etherchannel' when searching InfoCenter