Joseph,
I am assuming that you would like all your traffic to head up to the L3 network.
So you would want to add a route statement in your router that would take any traffic and send it to the next hop (Level 3).
The route statement looks like this:
ip route 0.0.0.0 0.0.0.0 6.59.186.61
I am assuming that you want to route traffic to client computer not NAT the workstations.
You should then have another interface that you can put the 6.59.192.224/27 network on. Usually this is the ethernet interface that plugs into your local network switch.
You would set the ip address to 6.59.192.225 leaving 29 hosts for your network.
The command that you run on the interface is:
ip address 6.59.192.225 255.255.255.224
config t
interface serial 0/0
description TO_LEVEL3
ip address 6.59.186.61 255.255.255.252
exit
ip route 0.0.0.0 0.0.0.0 6.59.186.62
interface fastethernet0/1
description TO_PC_OR_LAN
ip address 6.59.192.225 255.255.255.224
no shutdown
exit
exit
To get a client connected you would then use an ip address in the range of 6.59.192.226-254 the netmask would be 255.255.255.224 and your default gateway would be 6.59.192.225.
So the path of traffic would be:
client pc (6.59.192.254) -> router ethernet (6.59.192.225) -> router serial (6.59.186.62) ->
L3 serial (6.59.186.61) -> Internets
Hope that helps
