Subnetting is a way of partitioning a network at the IP level by dividing a block of addresses into a number of smaller sets.

The Subnet mask identifies which part of an IP address is network address and which part is host address.

In this above scenario there are 3 CBR Application has been created.

APP1_CBR - Wired Node A to Wired Node E

APP2_CBR - Wired Node B to Wired Node D

APP3_CBR - Wired Node A to Wired Node D

In this Applications APP1_CBR, APP2_CBR packets are getting transmitted. But APP3_CBR packets are not transmitted.

Because APP1_CBR is across 2 different Subnet/ Network which is connected via a router and hence transmission occurs.

APP2_CBR is within Subnet 2 transmission occurs via switch itself.

APP3_CBR from Subnet 1 to Subnet 2 which is connected via a layer 2 switch, is not being transmitted because a router is required to send packets across two networks.