Question On Showing of Protocols

I passed my ccna but there is still one thing I dont understand.

I set up 2 routers as WAN:

one is set as 10.1.1.1/30 and the other is WRONGLY set as 10.1.1.5/30.

Obviously they cannot ping each other.
However, when I use show ip int brief, the physical and protocols are displayed as up.

Shouldnt the protocol be down instead?? I dont understand,

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Comments

NetworkVeteran

hitmen wrote: »

one is set as 10.1.1.1/30 and the other is WRONGLY set as 10.1.1.5/30.
However, when I use show ip int brief, the physical and protocols are displayed as up.

IOS Output wrote:

router>show ip interface

Ethernet 0 is up, line protocol is up

When they say protocol, they mean line protocol. They're saying the data-link layer is up, not that the network-layer is up.

d6bmg

Up/Up means Physical Layer & data link layer is working.
They can't ping each other because they are in different subnet.
To ping two hosts in different subnet, you are going to need routing protocol.

I can't think of any easier explanation. Hope it makes the scenatio clear to you

Coolhandluke

d6bmg is correct. The fact that the interface is up/up simply means that the physical layer (interface) and the data layer are working (encapsulation types, HDLC, PPP etc). IP's are at layer 3 which an interfaces up/up status doesn't show.