Question 16906 – IP-Adress

The forwarding table of a router is shown below.

A packet addressed to a destination address 200.150.68.118 arrives at the router. It will be forwarded to the interface with ID _____?

Correct Answer: A

Question 1 Explanation:

We know IP & Subnet = subnetID to which given packet belongs to. So we will do an IP & Subnet mask and see if we are getting the same subnet ID or not and we will go for the longest prefix match.

So let’s first check subnet 1,
200.150.68.118 & 255.255.255.0 = 200.150.0.0, subnet ID matches

Now let’s check for subnet 2,
200.150.68.118 & 255.255.224.0 = 200.150.64.0, subnet ID matches

Now let’s check for subnet 3,
200.150.68.118 & 255.255.255.0 = 200.150.68.0, subnet ID matches

Now let’s check for subnet 4,
200.150.68.118 & 255.255.255.224 = 200.150.96.0, subnet ID do not match

subnet ID matches for interface 1,2, and 3 but since longest match is for interface 3 so our packet will be forwarded to interface 3