Hi,
how did you configure the interface on the catalyst?
To be more precise i assume you are running ios on the catalyst 2950. in that case i think you can configure the ethernet port on the switch as a routed port or a switched port.
If you want to use it as routed port you are configuring the real ethernet interface. If you use it as a switchport you need something like this:
interface fastethernet x
swichtport
switchport access vlan x
i am not the expert on cat2950 switches but that is something i would start to look at. If you say the
show mac-address-table does not show the mac address of your osa/2. if you can ping it i guess you can also see it in the arp table.
You should be able to move the ip address from the ethernet interface to a interface vlan x after you enabled the switchport.
Other ports on the cat2950 which are supposed to have llc2 stations running sna must be in the same vlan than the osa/2.
thanks....
Matthias