need configuration answer for cisco 1720 router

[mkzsm]

I already have a t1 serial 0 interface setup.

My second, serial 1 interface is not setup, and I want
to configure a Point-to-Point link between two Routers.
I'm not sure if all i have to type in the command line is on both sides of the router is:

RouterA:
-config t
int s1
ip unnumbered
ip add 192.168.0.1 255.255.255.255(PPP does not need a public ip)

RouterB:
-config t
int s1
ip unnumbered
ip add 192.168.0.2 255.255.255.255


Thanks for your help.

 

[IllegalOperation]

Your ip addresses on each serial interface are on the same subnet (your right they dont have to be public), so your config should work as far as the addressing goes. However, you would want to use a /30 for each link, instead of the 255.255.255.255 masks.

Your going to need to configure the actual PPP link itself on each interface also. For example, if you are using frame relay, you need to configure the dlci, lmi type, line coding, etc.

Youll obviously have to add routes if you want to communicate with different subnets. For example, lets say RouterB has a 192.168.1.0 subnet on its ethernet 0 interface. On RouterA, you would do...

ip route 192.168.1.0 255.255.255.0 192.168.0.2



Just out of curiosity, why the ip unnumbered?

 

[mkzsm]

well first my configuration was all out of order
but why i put ip unnumbered is because i was thinking
not to give an ip address to the serial interface because
i thought PPP is created by creating a subinterface, surely wrong on that part.
Im curious if the T1 goes down on Router A, and PPP is routing packets to get to the T1 on Router B which is what we have in mind of backup. Don't we have to enable NAT, because it is going from fake ip to real(public) ip.

 

[IllegalOperation]

"why i put ip unnumbered is because i was thinking
not to give an ip address to the serial interface because
i thought PPP is created by creating a subinterface, surely wrong on that part."


Actually, your technically right. You dont HAVE to create subinterfaces over a single PPP link, but its good to do so for administrative purposes. Where your wrong at is the ip unnumbered command. If you dont want to assign an ip address to the serial interface (and use subinterfaces instead), use the "no ip address" command instead of ip unnumbered.




Your last comments kind of confuse me, but if Im thinking what your thinking - then no you dont need to use NAT.