Question

The router can deliver packets directly over interfaces 0 and 1 or it can forward packets to Routers R2, R3, or R4. Describe what the router does with a packet addressed to each of the following destinations:
a. 128.96.39.10
b. 128.96.40.12
c. 128.96.40.151
d. 192.4.153.17
e. 192.4.153.90

Answer 1

Answer:

Following are the solution to this question:

Explanation:

In point A:

It applies the AND operation with the subnet-mask that is  

$=128.96.39.00001010 \ \ AND \ \ 255.255.255.10000000 \\\\= 128.96.39.0000000 \\\\= 128.96.39.0$

This corresponds to a 128.96.39.0 subnet. This is why the router sent the packet to 0.

In point B:  

It applies the AND operation with the subnet-mask that is $255.255.255.128$

$= 128.96.40.00001100\ AND \ 255.255.255.10000000 \\\\ = 128.96.40.0000000\\\\= 128.96.40.0$

This suits the 128.96.40.0 subnet. The router then sent R2 to the packet. The packet.

In point C:  

It  applies the AND operation with the subnet-mask that is $255.255.255.128$

$=128.96.40.10010111 \ AND \ 255.255.255.10000000 \\\\= 128.96.40.1000000\\\\= 128.96.40.128$

It  applies the AND operation with the subnet-mask  that is $255.255.255.192$

$= 128.96.40.10010111 \ AND \ 255.255.255.11000000 \\\\= 128.96.40.1000000 \\\\= 128.96.40.128$

All of the matches of its sublinks above.  

Its default R4 router was therefore sent to the router by router.

In point D:

It  applies the AND operation with the subnet-mask  that is $255.255.255.192$

$= 192.4.153.00010001 \ AND \ 255.255.255.11000000\\\\ = 192.4.153.0000000 \\\\= 192.4.153.0$

It matches the 192.4.153.0 subnet. It router has sent packet to R3 then.

In point E:

It  applies the AND operation with the subnet-mask  that is $255.255.255.128$

$= 192.4.153.01011010\ AND \ 255.255.255.10000000 \\\\= 192.4.153.0000000 \\\\= 192.4.153.0$

There, neither of the subnet inputs correlate with the ip address with the same subnet mask.

It  applies the AND operation with the subnet-mask  that is $255.255.255.192$

$=192.4.153.01011010\ AND \ 255.255.255.11000000 \\\\ = 192.4.153.0100000 \\\\= 192.4.153.64$

It does not correlate to the subnet entries for same subnet mask, and therefore neither of the entries matches their corresponding ip address entries.  

Mask of the subnet.  That packet would therefore be sent to the default R4 router by the router.