Question 58

All prefixes begin with 10.1.1., so we can express each prefix by the range of its 4th octet:

• 10.1.1.0/24: $0 \text{ to } 255$ (prefix length 24) $\rightarrow$ R1
• 10.1.1.128/25: $128 \text{ to } 255$ (prefix length 25) $\rightarrow$ R2
• 10.1.1.64/26: $64 \text{ to } 127$ (prefix length 26) $\rightarrow$ R3
• 10.1.1.192/26: $192 \text{ to } 255$ (prefix length 26) $\rightarrow$ R4

Applying Longest Prefix Match (LPM) to the 5 hosts (20 packets each):

1. 10.1.1.16: matches only /24 $\rightarrow$ R1
2. 10.1.1.72: matches /24 and 10.1.1.64/26 $\rightarrow$ longest is /26 $\rightarrow$ R3
3. 10.1.1.132: matches /24 and 10.1.1.128/25 $\rightarrow$ longest is /25 $\rightarrow$ R2 (20 packets)
4. 10.1.1.191: matches /24 and 10.1.1.128/25 $\rightarrow$ longest is /25 $\rightarrow$ R2 (20 packets)
5. 10.1.1.205: matches /24, 10.1.1.128/25, and 10.1.1.192/26 $\rightarrow$ longest is /26 $\rightarrow$ R4

Total packets forwarded via R2 $= 20 + 20 = 40$.