Aggregating network links

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Each physical appliance can bond network interfaces to prevent single point of failure or aggregate links for high-performance applications.

Table 1. Supported network interface bonding modes
Mode	Purpose	Description
`active-backup`	Redundancy using active-backup fail-over to increase availability	Each link can be connected to a different switch to prevent single point of failure. Under normal conditions, one link is in an active state, passing traffic. The second link is in the backup state, with no traffic sent through that link. When active link fails, the second link takes over and transitions to the active state. If required, a single link in the bonded pair can be configured as primary. If configured using the channel command, the primary link is always active if possible. This allows the customer to control which bonded link is used as active under normal conditions. This functionality can be changed via the `bond_primary_reselect` option: `always` (default): bond will always use and prefer the 'primary' adapter if it is available `failure`: if the primary adapter fails and comes back online, the bond will not switch back to the 'primary' adapter until the secondary adapter is taken offline Typically, the redundant bonding mode does not require any specific switch configuration.
`802.3ad`	Balance using link aggregation to increase throughput	Supported standard is Link Aggregation Control Protocol (LACP) defined in IEEE802.1ax, previously IEEE802.3ad. Under normal conditions, both links are in an active state passing traffic. If one link fails, the second link stays active and keeps passing traffic. When both links are active, the transmit hash policy selects the link for outgoing traffic. IBM® Cloud Object Storage System appliances support the following transmit hash policies in the balanced bonding mode:
		Policy Options	Frame Fields in Hash	Command
		`Data Link Layer [2] (default)`	Source, destination MAC addresses	`[source,console] --- # channel data bond_xmit_policy layer2 ---`
		`Data Link + Network Layer [2+3]`	Source, destination MAC and IP addresses	`[source,console] --- # channel data bond_xmit_policy layer2+3 ---`
		`Network + Transport Layer [3+4]`	Source, destination IP addresses and TCP/UDP ports	`[source,console] --- # channel data bond_xmit_policy layer3+4 ---`

Note: A single connection or TCP flow can only span one link, no matter which hash policy is used.

Data Link Layer [2] is the default transmit hash policy. Each hash policy has its advantages and disadvantages.

The balanced bonding mode requires specific switch configuration that enables LACP mode.

The hash policy only controls the outgoing traffic from the appliance. The directly attached network switch controls the incoming traffic. The number of supported switch hash polices depends on type of network switch is used.

Tip: The decisions as to which hash policy to use can significantly impact overall system performance.

Example 1. Bonding Network Interfaces

Two NICs, identified as eth0 and eth1, will be bonded to increase the collective throughput.

Log in to the appliance as localadmin.
```
# login
```
Enter edit mode to modify the current settings.
```
# edit
```
Set the ports eth0 and eth1 for this channel.
```
# channel data port eth0, eth1
```
Configure the bond for load balancing.
```
# channel data bonding 802.3ad
```
Configure xmit (transmit) hash policy.
```
# channel data bond_xmit_policy layer2
```
Save the new settings.
```
# activate
```
Reboot the appliance
Log in as localadmin.
```
# login
```
Verify the settings are complete and correct.
```
# channel list
```
Ping the network gateway to check connectivity.
```
# ping <gateway ip>
```
For IPv6 network gateways, use ping6:
```
# ping6 <gateway ip>
```