2.3.b Implement and troubleshoot PPP

ipexpert_ppp_notes

observe the diagram. hdlc is cisco’s default serial protocol.

we have l3 connectivity:

R1#ping 192.168.12.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.12.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/28/60 ms

and the routing table is as it should be:

R1#sh ip route | b Gate
Gateway of last resort is not set

C    192.168.12.0/24 is directly connected, Serial3/0

or:

R1#sh ip route connected
C    192.168.12.0/24 is directly connected, Serial3/0

note /24 in the routing table and in the output of sh ip route connected

introduce ppp encapsulation on both ends:

R2(config-if)#encap ppp
R2(config-if)#do sh int s3/0
Serial3/0 is up, line protocol is up
Hardware is M4T
Internet address is 192.168.12.2/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP Open
Open: IPCP, CDPCP, crc 16, loopback not set

the routing table has changed to the default for ppp. note two connections and the  /32:

R2#sh ip route | b Gate
Gateway of last resort is not set

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks
C       192.168.12.0/24 is directly connected, Serial3/0
C       192.168.12.1/32 is directly connected, Serial3/0

this is expected. however, if for some reason there is a task that requires the mask to show in the routing table as configured on the interface, this command can be used:

R2(config-if)#no peer neighbor-route
R2(config-if)#shut
R2(config-if)#no shut
R2(config-if)#
R2(config-if)#do sh ip route conn
C    192.168.12.0/24 is directly connected, Serial3/0

R2#sh ip route | b Ga
Gateway of last resort is not set

C    192.168.12.0/24 is directly connected, Serial3/0
R2#

do not forget to issue shut, no shut