Hi everybody,

I have a dilemma regarding the number of networks in HACMP. If i am correct, the number of networks in HACMP is influenced by the netmask. If i have, let's say, the netmask 255.255.255.0 , and all network interfaces configured correctly, I'll have defined net_ether_01. Different netmask, lead to net_ether_02 and so forth.
If service ip address can be assigned to only one network, what is the use of net_ether_02,net_ether_03, etc ?
A link to some documentation which clearly explains the network concept in HACMP (the official IBM doc is not very clear when it explains the network concept and how HACMP discover HB rings) would be much appreciated .

Hi iulian,

I don't get what your problem is.
If for example you have a node that hosts 3 applications (meaning 3 ServiceIPs) and each is menat for a different network. It makes perfectly sense.
Or if you want one application for internal AND external use.
You have two different netmasks (and interfaces), one ServiceIP for internals (hosted on net_ether_1) and one ServiceIP for externals (hosted on net_ether_2).
I hope I didn't write anything wrong.

Kind regards

Hello iulian,

in HACMP there is a rule that one network can only have one network mask. During setup of the cluster HACMP puts adapters with same netmask to one HACMP network. This can be changed later using the extended config.
The service addresses are assigned to an HACMP network which defines to which addapters the service addresses may be given. How many HACMP networks you need depends on the fact whether the service addresses have to be given to differnent adapters and the service addresses having the same netmask.

Kind Regards

Hello Claus,

Thank you for explanation.

An HACMP network generally defines the adapters that can directly communicate among each other and can caryy the service IP address. The netmask is only one criteria whether adapters belong to the same network or not. Another, far more important criteria is if the adapters are really reachable (same LAN or same VLAN).

If you have 4 adapters of which 2 are in different VLANS, this will lead to two HACMP networks as well as HA will verify the reachability of all adapters of a network prior creating it (no matter which IP address is configured on top). This is done through IP source routing through RSCT.