A.2 through 1001 B.1 through 1001 C.1 through 1002 D.2 through 1005
A.2001:0000:130F::099a::12a B.2002:7654:A1AD:61:81AF:CCC1 C.FEC0:ABCD:WXYZ:0067::2A4 D.2004:1:25A4:886F::1
A.(config-if)#authentication ppp chap fallback ppp B.(config-if)#authentication ppp chap pap C.(config-if)#ppp authentication chap pap D.(config-if)#ppp authentication chap fallback ppp