The cross-over cable thing should help with this.
It's because opensmd will only attach to (and use) one port on a server. By default it attaches to the first port of the first card it finds. Port 0 for you.
When you have port 0 on a server connected to port 0 on another server, with opensmd running on both... what happens is that the first opensmd to start initialises port 0 (ignoring port 1), then it communicates to the other servers' card (port 0) through this connection, initialising that too. With that first working link established, port 0 (on both ends) is marked as "ACTIVE" and things can communicate over it.
When the opensmd on the other node starts up, it tries to attach to port 0. But it notices the link is already active with another opensmd running on the network. So, it doesn't proceed with loading and just shuts itself down. (leaving the existing ACTIVE link and other opensmd all still running fine)
This is why having port 0 connected to port 0, with port 1 connected to port 1 (and opensmd on both) results in only the port 0 link being active. The port 1 link never comes up because neither opensmd tries using it.
When you do it cross over style (port 0 to port 1 for both servers), both of the opensmd's get their own port 0 and successfully talk to port 1 on the other box, then bring up their link as "ACTIVE".
That being said, this is just how things run when they're going by defaults and is the easiest way to set things up. You can tell opensmd to connect to a different port (not port 0) if you want, by adjusting the config file. But then you have to maintain the configuration files, etc. Personally, I like to keep things simple where possible, and leave complicated stuff for when it's actually necessary.
Does that help?
(note - edited for typo and clarity fixes)