Subnet routing requirements in PowerHA SystemMirror
A subnet route defines a path, defined by a subnet, for sending packets through the logical network to an address on another logical network.
AIX® allows you to add multiple routes for the same destination in the kernel routing table. If multiple matching routes have equal criteria, routing can be performed alternatively using one of the several subnet routes. It is important to consider subnet routing in PowerHA® SystemMirror® because of the following considerations:
- PowerHA SystemMirror does not distinguish between logical network interfaces that share the same subnet route. If a logical network interface shares a route with another interface, PowerHA SystemMirror has no means to determine its health. For more information on network routes, see the AIX man page for the route command.
- Various constraints are often imposed on the IP-based networks by a network administrator or by TCP/IP requirements. The subnets and routes are also constraints within which PowerHA SystemMirror must be configured for operation.
Note: You should have each communication interface on a node that
belongs to a unique subnet, so that PowerHA SystemMirror can monitor
each interface. This is not a strict requirement in all cases and
depends on several factors. For example, when there is only one network
interface per node, such as in a virtual network environment, the
boot and service IP addresses can be on the same subnet because there
is a single subnet route. If unique subnets are required, PowerHA SystemMirror cluster verification
will flag this as an error.