Thats only needed on a router using DSL connections, for the most part.
If its a cable router he doesn't even need the PPPoE/PPPoA password.

He is talking about the login password to enter the configurations on the router.
Usually routers have default passwords like:

User: admin
Password: admin

Thats what he is trying to do. Get inside the internal configurations on the router using the web browser, where he is automatically asked for an administration login (nothing to do with the ISP connection login). He only wants to portforward some ports to be able to host game serves or/and use some other software directly without having the need to indirectly relay the connection.

So ThePz, try these:

if its an SMC router:
user: admin (if it even asks for one, most smc routers don't ask you for the username)
password: smcadmin

Some other common default passwords:

user: admin
password: password

user: root
password: root

user: root
password: admin

user: Administrator
password: admin (or) password

Good luck... If nothing works you can reset the router, if you know how to properly configure it.. If you have a Cable Internet (Coaxial) it'll be easier to configure since you most likely don't need any configurable authentication.