PT Bug?

Alceo

I have
PCA 192.168.1.2/16
PCB 192.168.2.2/24
separated by a router used as a default gateway.

For my understanding PCA shouldn't be able to ping PCB
For PCA, PCB is in the same subnet so it should use an ARP to learn it's MAC address, it shouldn't forward the packet to the router.

In PT PCA ping PCB, is this a bug or Am I missing something?

rob42

What IP Addresses/Masks have you set on the Router interfaces?

Jon_Cisco

Can you watch the packets and see if the router is forwarding it. For me the best part of packet tracer was the ability to watch the network traffic to understand how it was moving.

Alceo

Just to check if it was a bug I set up GNS3 with two Virtual Machines connected to two differerent LAN cards:


To my surprise a ping from 192.168.1.2 to 192.168.2.2 worked just fine despite the subnet mask.

Here is why:

192.168.1.2 sends an ARP for 192.168.2.2 and Router1 responds with the mac address of it's own interface facing 192.168.1.2

Is this a Cisco thing or all routers do the same?

networker050184

Depends on your device, version and config. That's called proxy ARP.

mikeybinec

I assume you mean this topology



If you look at the routing table (sh ip ro) you'll see both networks are directly connected and network masks or Class A vs Class B, etc doesn't matter.. The router knows where to send the traffic



regards

dontstop

rob42 wrote: »

What IP Addresses/Masks have you set on the Router interfaces?

Interested in this too.

Alceo

The one in the picture 192.168.1.1/24 and 192.168.2.1/24
The thing I was missing is the one indicated by networker, the proxy arp function.