Host Integration Server is by default configured to use ‘smart multihoming’. When using smart multihoming, the Host Integration Server (HIS) will send all his available IP addresses to the clients. The SNA client will use the address from the list with addresses received from the server that is closest to its own subnet or IP address.
In some scenarios smart multihoming can cause some problems. What if one of the IP addresses received from the HIS server is not reachable (e.g. an IP address that is used to link to a separate network)? In that case the client will try to connect to one of the other address received from the HIS server. This only happens after a delay (default 45 seconds). After the delay the client will connect to the IP address that connects successfully.
This delay when connecting to the server is not a desired behavior.
How do we fix this?
On the client we can disable smart multihoming. To do this, make sure that this registery key ‘ReadjustMultihomedAddresses’ is set to ‘NO’. If the key does not exist, create it. The location of this registry key should be: ‘HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Snabase\Parameters\SnaTcp’.
If smart multihoming is disabled on our client, the new behavior is as follows: the client will try to connect to a server IP address in the order as the client received them from the server. Again, this causes problems… What if the IP address that is not reachable appears first in the list? We will again see a long delay when connecting to the server. Luckely we can fix this!
Host integration server uses the network bindings to determine in what order to present its IP addresses to the client. You can find the network binding on the ‘Network Connections’ sceen, ‘Advanced’ menu option, ‘Advanced Settings…’, then ‘Adapters and Bindings’ tab. On that tab page, every network connection is listed and we are able to change the order in which they appear. Adapt the order to your needs (reachable IP’s first!!!). Host Integration Server will use the order specified here to send it’s IP list to the client.
Now that both steps are done (disable smart multihoming AND change the network bindings on the server), the client will no longer experience a delay when connecting to the HIS server.
Peter Borremans