Mismatched IP Addresses
A catchy botheration to atom is if you accept HDLC or PPP configured on your consecutive interface but
your IP addresses are wrong. Things assume to be aloof accomplished because the interfaces will appearance that
they are up. Booty a attending at Figure 11.6, and see whether you can see what I mean; the two
routers are affiliated with altered subnets—router Pod1R1 with 10.0.1.1/24 and router
Pod1R2 with 10.2.1.2/24.
Mismatched IP addresses
This will never work. But as I said, booty a attending at the output:
Pod1R1#sh int s0/0
Serial0/0 is up, band agreement is up
Hardware is PowerQUICC Serial
Internet abode is 10.0.1.1/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, loopback not set
Keepalive set (10 sec)
LCP Open
Open: IPCP, CDPCP
See that? The IP addresses amid the routers are wrong, but the articulation looks like it’s working
fine. This is because PPP, like HDLC and Frame Relay, is a layer-2 WAN encapsulation
and doesn’t affliction about IP addresses at all. So yes, the articulation is up, but you can’t use IP beyond this
link back it’s misconfigured.
To acquisition and fix this problem, you can use the appearance running-config or appearance interfaces
command on anniversary router, or you can the appearance cdp neighbors detail command:
Pod1R1#sh cdp neighbors detail
-------------------------
Device ID: Pod1R2
Entry address(es):
IP address: 10.2.1.2
You can appearance and verify the anon affiliated neighbor’s IP abode and again break your
problem.
Before we move assimilate Frame Relay, let’s booty a attending at PPPoE.
hostname Pod1R1
username Pod1R2 countersign cisco
interface consecutive 0
ip abode 10.0.1.1 255.255.255.0
encapsulation ppp
ppp affidavit chap
hostname Pod1R2
username Pod1R1 countersign cisco
interface consecutive 0
ip abode 10.2.1.2 255.255.255.0
encapsulation ppp
ppp affidavit chap