can't ping the WAN IP of a router

[metaclay]

I learned to use cisco packet tracer and found something confusing. So i tried building this simple lan setup :

PC 192.168.1.10 ---> switch ---->  router A (192.168.1.1 / 10.0.0.5) ------> router B (10.0.0.4)

The router A has LAN IP 192.168.1.1 and WAN IP 10.0.05

In my setup :

PC IP is 192.168.1.10/24 and set gateway to 192.168.1.1

i can ping from PC to 192.168.1.1 (LAN IP of router A) 

i can ping from PC to  10.0.0.5 (WAN IP or router A)

The problem is : if i disconnect router B from router A

i no longer can ping to 10.0.0.5 . Why is it ? why it depends on the connection of router B while that IP (10.0.0.5) has nothing to do with router B

If i reconnect again router A and B, then i now can ping from PC to 10.0.05

How does it actually works ?

Thanks

[Seb Rupik]

Hi there,

When you remove routerB you are also removing the connection to the routed interface (10.0.0.5) on routerA, this will put the interface status to down. You should be able to confirm this with the command sh int status . This is why you cannot ping 10.0.0.5 .

cheers,

Seb.

[Giuseppe Larosa]

Hello @metaclay ,

I don't know the exact detail but if you used a serial interface for the WAN when the other side is disconnected also RA side will go down.

This happens also in real world with routers that are directly connected to each other.

On the other hand if your WAN is an ethernet anfd you place a LAN switch on the path when RB is disconnected RA will stay up.

Hope to help

Giuseppe