network-programmingippingmac-addressarp

Ping request fails with wrong ARP?

I spent hours on this but with no success, I am trying to ping: 172.23.67.188 (Router B external ip) from A-Host.

So in A-Host terminal I typed:

ping 172.23.67.188 -c 3

But ping fails with 100% loss, so I ran it again with tcpdump and got the following output:

enter image description here

Why I don't see arp request like this:

arp who was 172.23.67.188 tell 192.168.11.188

What is causing this ping to fail? (Note A host can ping itself, Router A both internal and external ip)

Here is a diagram:

enter image description here

Please Note: x=187, y=188

Solution

  • You won't see an ARP request like "arp who was 172.23.67.188 tell 192.168.11.188" because 172.23.67.188 and 192.168.11.188 are on different networks, so the ARP should be for the router 192.168.11.188 uses to reach 172.23.67.188. Also note that both these addresses are not globally routable since they are in the private address space.