Your route(s) will fall into the default if there is no other route specified. So in looking at the route table, I suspect it would look something like this.
#netstat -rn
default 191.0.3.2 UG 2 3354 en0
127 127.0.0.1 U 9 3247 lo0
xxx.xxx 191.0.10.0 U 3 342 en0
Whatever network addresses you have in xxx.xxx will be routed to 191.0.10.0. If xxx.xxx was 191.0.10 and you had all yur dial up connections assigned something on the 191.0.10 network, then all the dial up connections would route to 191.0.10.0. If you took away that route statement, all the dial up connections would fall under the default route statement.