What are the ways of getting IP layer address e.g. ip address on an inteface using PPP without putting an IP address directly on an interface?

Scenario: Two routers connected back-to-back via serial inteface.

Dynamips config:

# Simple lab P2P via Serial
[localhost]
[[3640]]
idlepc= 0x604f96b4
image = \IOS\c3640-js-mz.124-19a\c3640-js-mz.124-19a.extracted.bin <<= edit this!
ram = 160
[[ROUTER R1]]
s1/0 = R2 s1/0
console = 2001
model = 3640
[[router R2]]
console = 2002
model = 3640

The following are the methods of geting this done:

1. IP unnumbered- can use HDLC, PPP on layer 2
2. Multilink PPP
3. PPP IPCP
4. PPP over Frame-Relay

Answers: Configs on next post.