PPP PAP and CHAP example

in the configuration below, I have configured PAP and CHAP and it worked in both cases, however I used one router as Server and one as Client.
PPP Configuration
PPP with PAP authentication:
in this configuration R1 is PAP Server and R2 is PAP client

R1(config)#int s1/0
 R1(config-if)ip address
 R1(config-if)#encapsulation ppp 
 R1(config-if)#ppp authentication pap
 R1(config)#username R2 password cisco

R2(config)#int s1/0
R2(config-if)ip address
R2(config-if)#encapsulation ppp 
R2(config-if)#ppp pap sent-username R2 password cisco


PPP with CHAP authentication:
in this configuration R1 is CHAP Client and R2 is CHAP Server

R1#configure terminal
R1(config)#interface serial 1/0
R1(config-if)ip address
R1(config-if)#encapsulation ppp 
R1(config-if)#ppp chap hostname R1
R1(config-if)#ppp chap password cisco

R2#configure terminal
R2(config)#username R1 password cisco
R2(config)#interface serial 1/0
R2(config-if)ip address
R2(config-if)#encapsulation ppp
R2(config-if)#ppp authentication chap


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 I believe in real world there could be scenarios where there is one server authenticating multiple clients or multiple servers authenticating each others.

I guess in the scenario where one server is authenticating multiple clients , we might just need to add the following line on the server for as many clients as we have,  correct me if I am wrong:

RouterServer(config)#username client1 password cisco
RouterServer(config)#username client2 password cisco2
RouterServer(config)#username client3 password cisco3
but what about the scenario when 2 servers authenticate each other? can someone post an example ?

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Qlemo"Batchelor", Developer and EE Topic AdvisorCommented:
Often it is the same - with PPP one site is the client (initiator), and the other the server (responder). For authentication there is a user as is with your example.

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jskfanAuthor Commented:
Thank you
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