Types of distribution for service IP label aliases
You can specify in SMIT different distribution preferences for the placement of service IP label aliases.
The types of distribution preferences follow.
| Type of distribution preference | Description |
|---|---|
| Anti-collocation | This is the default. PowerHA® SystemMirror® distributes all service IP label aliases across all boot IP labels by using a least-loaded selection process. |
| Collocation | PowerHA SystemMirror allocates all service IP label aliases on the same network interface card (NIC). |
| Anti-collocation with persistent labels | PowerHA SystemMirror distributes
all service IP label aliases across all active physical interfaces
that are not hosting the persistent IP label. PowerHA SystemMirror places the
service IP label alias on the interface that is hosting the persistent
label only if no other network interface is available. Note: If
you did not configure persistent IP labels, PowerHA SystemMirror lets you select
the anti-collocation with persistent distribution preference, but
it issues a warning and uses the regular anti-collocation preference
by default. |
| Collocation with persistent labels | All service IP label aliases are allocated on the same NIC
that is hosting the persistent IP label. This option might be useful
in VPN firewall configurations where only one interface is granted
external connectivity and all IP labels (persistent and service) must
be allocated on the same interface card. Note: If you did not
configure persistent IP labels, you can use PowerHA SystemMirror to select the
collocation with persistent distribution preference, but it issues
a warning and uses the regular collocation preference by default. |
 Collocation with persistent label and source |
Service labels are mapped to the same physical interface that
currently has the persistent IP label for this network. This option allows you to choose one service
label as the source for outgoing communication. The service label chosen in the next field will be
used as the source address. |
| Anti-collocation with source | Service labels are mapped by using the anti-collocation preference. If there are not enough adapters, more than one service label can be placed on one adapter. With this choice one label is chosen as the source address for outgoing communication. The interface label chosen in the Source IP Label for outgoing packets field is the source address. |
| Collocation with source | Service labels are mapped by using Collocation preference. With this choice one service label is chosen as the source address for outgoing communication. The interface label chosen in the Source IP Label for outgoing packets field is the source address. |
| Anti-Collocation with persistent label and source | Service labels are mapped by using the anti-collocation with persistent preference. One service address can be chosen as a source address for the case when there are more service addresses than boot adapters. |
The following rules apply to the distribution preference:
- If there are insufficient interfaces available to satisfy the preference, PowerHA SystemMirror allocates service IP label aliases and persistent IP labels to an existing active network interface card.
- If you did not configure persistent labels, PowerHA SystemMirror lets you select the collocation with persistent and anti-collocation with persistent distribution preferences, but it issues a warning and uses the regular collocation or anti-collocation preferences by default.
- You can change the IP labels distribution preference dynamically: the new selection becomes active during subsequent cluster events. PowerHA SystemMirror does not interrupt the processing by relocating the currently active service IP labels at the time the preference is changed.
When a service IP label fails and another one is available on the same node, PowerHA SystemMirror recovers the service IP label aliases by moving them to another NIC on the same node. During this event, the distribution preference that you specified remains in effect.