GO Classes Test Series 2024 | Mock GATE | Test 14 | Question: 51

Question

Consider the following forwarding table in a router that uses longest prefix matching to forward packets. Assume that 4-bit addressing is used.
$$
\begin{array}{c|c}
\hline \text{prefix} & \text{interface} \\
\hline X & 1 \\
Y & 2 \\
\text{Otherwise} & 3 \\
\hline
\end{array}
$$
We know that packets with an address of 0100 are forwarded to Interface 1 and packets with an address of 0010 are forwarded to Interface 2.

Which of the following CAN be the values for $X$ and $Y?$

• A. $X=0$ and $Y=00$
• B. $X=01$ and $Y=00$
• C. $X=010$ and $Y=00$
• D. $X=00$ and $Y=0$

Comments

@Sachin Mittal 1 sir, How is option A correct?
How can prefix for 1 be the subset of another?

---

It is definitely possible, what is problem in that ?

Answer 1

p1 = 0100

p2 = 0010

A) 0,00->P1-X,P2-Y

B) 01,00->P1-X,P2-Y

C) 010,00-> P1-X,P2-Y

D) 00,0 -> P1-Y,P2-X

 

SO A,B,C can be the correct prefit