Can't ping router 3 Why?

dave dunlap

Hi
I am making a GNs3 lab

I have 3 routers all the same network

r1 s0/0 172.16.1.1

r2 s0/0 172.16.1.2
r2 s0/1 172.16.1.3

r3 s0/0 172.16.1.4

if I do: show ip int brief all interfaces are up up
if I do: show cdp neighbors r1 neighbors shows r2.
r2 neighbors show r1 r3
r3 neighbors show r2
r1 can ping r2 int s0/0, & s0/1, but not r3
r2 can ping r1 but not r3
r3 can not ping any

I try:
r1(config)#int s0/0 <cr>
r1(config-if)#encapsulation hdlc <cr>
samr for r2, & r3.
!
but still no r3 ping r2.
why?
because is same network?
but I am doing Train signal ccna securety 5th video Layer 3,
we are setting up NTP and he checks connectivity and he can ping.
why?
what protocol do I need to configure?

thanks for the help
dave

Monkerz

Might want to refigure your networks. R2 will not work with two interfaces in the same subnet.