How to Router to Router connection

Router to Router  connection

Step1

Add caption

R# show  ip   interface    brief   <┘ (check interface and IP address)

Step2

R# show  interface  serial 0/0   <┘ (check network prefix and encapsulation )

    NOTE:   By default encapsulation protocol is  HDLC and must be same on both sides

          To change encapsulation :-

          R(config)# interface   s0/0    <┘

          R(config-if)# encapsulation  hdlc    <┘

                             #^Z

Step3

R# show   controllers    serial  0/0    <┘ (check serial cable)

If showing DTE, then do nothing

If showing DCE,  then   R(config)# interface   serial  0/0   <┘

                                      R(config-if)# clock   rate   64000  <┘

                                                          # ^Z

NOTE:

We have to set encapsulation and clock rate  for serial interface only

Troubleshooting for router to router connection

R# show   ip   interface   brief   <┘

There are 4 conditions for troubleshooting :-

Condition I

Line  Status is UP  and   Protocol  is  Up

It means everything is OK, Physical and Data Link layer are working properly

It is problem of IP addressing only.

Condition II

Line  Status  is Up and Protocol is Down

It means    (i)     Mismatch encapsulation

                   (ii)    Clock rate 64000 is not set

Condition  III

Line Status is Down and Protocol is Down

It means    (i)  Serial interface of remote router is Shutdown

                   (ii) Serial cable is faulty

                   (iii)Serial interface card is faulty

Condition  IV

Line  Status is Administratively  Down,   Protocol   is  Down

It means  Serial interface of local router is Shutdown