Configure
To configure a Point-to-Point link, you will configure the serial interface just like you would an Ethernet interface. In addition, you need to use the no shutdown command because interfaces are down by default on a router. The other difference is that you need to have a clocking mechanism in place. Clocking takes place on the Data Communications Equipment (DCE).
Router#configure terminal Router(config)#interface serial 0/0/0 Router(config-if)#ip address ip-address subnet-mask Router(config-if)#no shutdown Router(config-if)#end
The default encapsulation type is High-Level Data Link (HDLC) protocol. To change it, you specify while in the interface configuration mode.
Router#configure terminal Router(config)#interface serial 0/0/0 Router(config-if)#encapsulation ppp Router(config-if)#end
Verify
The following verification command identifies the Data Terminal Equipment (DTE).
Router#show controllers serial 0/0/0 | include V.35 DTE V.35
The following verification command identifies the Data Communications Equipment (DCE).
Router#show controllers serial 0/0/0 | include V.35 DCE V.35, clock rate 2000000
This next command will display the properties for the serial interface. From it, we can see the encapsulation protocol is set to High-Level Data Link (HDLC) protocol.
Router#show interfaces serial 0/0/0 Serial0/0/0 is up, line protocol is up Hardware is WIC MBRD Serial Internet address is 192.168.255.2/30 MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set
This next command is to verify that the Point-to-Point protocol encapsulation is set on the serial interface. LCP in the output is for Link-Control Protocol.
Router#show interfaces serial 0/0/0 Serial0/0/0 is up, line protocol is up Hardware is WIC MBRD Serial Internet address is 192.168.255.2/30 MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, LCP Open Open: IPCP, CDPCP, loopback not set
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