Note: HDLC is the default serial encapsulation. Both ends of serial link must be configured the same.
Configure PPP Encapsulation for Serial 0 at both R1 and R2
R1 (config) # int s0/0/0
R1 (config-if) # encapsulation ppp / encap ppp
Note: If OSPF was already configured, the link will go down, until the other end has also been configured as PPP and the link should go up.
R2 (config) # int s0/0/0
R2 (config-if) # encapsulation ppp / encap ppp
R1 (config) # do show int s0/0/0
Configure PPP (with CHAP or PAP Authentication) at Serial 0 for both R1 and R2
Hostname = username
password = cisco
R1 (config) # username R2 password cisco (or secret class)
R1 (config) # int s0/0/0
R1 (config-if) # encapsulation ppp / encap ppp
R1 (config-if) # ppp authentication chap / ppp auth chap (or pap)
If secret class is used,
R1 (config-if) # ppp chap (or pap) sent-username R1 password cisco
Note: If OSPF was already configured, the link will go down, until the other end has also been configured as PPP and the link should go up.
R2 (config) # username R1 password cisco (or secret class)
R2 (config) # int s0/0/0
R2 (config-if) # encapsulation ppp / encap ppp
R2 (config-if) # ppp authentication chap / ppp auth chap (or pap)
If secret class is used,
R1 (config-if) # ppp chap (or pap) sent-username R1 password cisco
R1 (config) # do show int s0/0/0
