Hi
Just a wild guess, but maybe the command is only available in a later software release. I dont have a 10508 switch to test it.
Normally a config should be like this example:
interface Route-Aggregation1
ip address 10.0.0.1 255.255.255.252
link-aggregation mode dynamic
#
interface GigabitEthernet1/0/1
port link-mode route
port link-aggregation group 1
#
interface GigabitEthernet1/0/2
port link-mode route
port link-aggregation group 1
You can also use the vlan interface like i explained in the first post if your switch doesn't support route aggregation.
Kind regards