Reduce IP addressing errors in lab environment

One of the most tedious tasks in the initial lab setup (at least for me) is the IP address configuration, which usually includes a number of typos and mixups on the WAN links. You can simplify then WAN address configuration if you configure only one end of the WAN link and let PPP do the rest. For example, you could use the following configuration to configure WAN link on your core router …
hostname Core-2
interface Serial1/0
 description link to POP
 ip address
 encapsulation ppp
 peer default ip address
… and use IPCP negotiation on the POP router to pick up the WAN IP address:
hostname POP
interface Serial1/0
 description link to Core-1
 ip address negotiated
 encapsulation ppp

You should not configure no peer neighbor-route on the router that gets dynamic IP address, as the subnet mask is not assigned with IPCP; you need the IPCP-generated host routes if you want to do hop-by-hop telnet between the routers.


  1. Hi Ivan

    What I would like to know is, on my PPP negotiated ADSL connection, how the ISP assigns me a /32 ip address.

    sh int dialer 0
    Dialer0 is up, line protocol is up (spoofing)
    Hardware is Unknown
    Description: $FW_OUTSIDE$
    Internet address is 124.1XX.XXX.XXX/32
    MTU 1500 bytes, BW 56 Kbit, DLY 20000 usec,
    reliability 255/255, txload 71/255, rxload 168/255
    Encapsulation PPP, loopback not set
    Keepalive set (10 sec)
    DTR is pulsed for 1 seconds on reset
    Interface is bound to Vi2
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