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Exam CISSP topic 1 question 257 discussion

Actual exam question from ISC's CISSP
Question #: 257
Topic #: 1
[All CISSP Questions]

Two computers, each with a single connection on the same physical 10 gigabit Ethernet network segment, need to communicate with each other. The first machine has a single Internet Protocol (IP) Classless Inter-Domain Routing (CIDR) address of 192.168.1.3/30 and the second machine has an IP/CIDR address
192.168.1.6/30. Which of the following is correct?

  • A. Since each computer is on a different layer 3 network, traffic between the computers must be processed by a network bridge in order to communicate
  • B. Since each computer is on the same layer 3 network, traffic between the computers may be processed by a network router in order to communicate
  • C. Since each computer is on the same layer 3 network, traffic between the computers may be processed by a network bridge in order to communicate
  • D. Since each computer is on a different layer 3 network, traffic between the computers must be processed by a network router in order to communicate
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️

Comments

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Stevooo
Highly Voted 1 year, 7 months ago
Selected Answer: D
These are two different IP subnets, hence should require a router for interconnectivity. However, 192.168.1.3/30 is a broadcast IP in that subnet and doesn't seem valid.
upvoted 20 times
dm808
1 month ago
lol 192.168.1.6 /30 is also a broadcast address
upvoted 1 times
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jackdryan
11 months, 2 weeks ago
D is correct
upvoted 1 times
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sphenixfire
1 year, 4 months ago
Smile i thougth the same ;D
upvoted 1 times
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Nabs1
Highly Voted 1 year, 7 months ago
Selected Answer: D
How is B showed as the correct answer is beyond me. These are 2 separate subnets with one being a broadcast IP address which means that even the question is wrong.
upvoted 9 times
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GPrep
Most Recent 3 months, 3 weeks ago
Selected Answer: B
(Previous comment didn't have the vote tallied) - They ARE on the same L3 network but different L2 networks. Given that L2 is implied in the subnetting, they DO need a router to communicate. Its all in the wording (these questions are all tricky). B is the correct answer as a result (very misleading). The broadcast network thing is a little weird. Had the answers stated L2 instead of L3, D would be correct.
upvoted 1 times
LVQ
3 months, 2 weeks ago
IP address routing does not happen on the data link layer , L2. A network's boundaries are within the network and broadcast IP. Both Ip addresses are a part of separate networks. 1 subnet = 1 L3 network.
upvoted 1 times
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GPrep
3 months, 3 weeks ago
They ARE on the same L3 network but different L2 networks. Given that L2 is implied in the subnetting, they DO need a router to communicate. Its all in the wording (these questions are all tricky). B is the correct answer as a result (very misleading). The broadcast network thing is a little weird. Had the answers stated L2 instead of L3, D would be correct.
upvoted 1 times
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YesPlease
4 months, 1 week ago
Selected Answer: D
Answer D) Devices are on different subnets....(and the first is calculated wrong) so they need a device to communicate with. Both Bridges and Routers can help connect the devices on separate networks, but the question clearly states LAYER 3, so it must use a ROUTER. Bridges are LAYER 2
upvoted 1 times
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Soleandheel
4 months, 2 weeks ago
Given the IP addresses 192.168.1.3/30 and 192.168.1.6/30, which have different network portions, the correct answer is: D. Since each computer is on a different layer 3 network, traffic between the computers must be processed by a network router in order to communicate.
upvoted 1 times
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BoyBastos
8 months ago
Selected Answer: D
Different subnet
upvoted 1 times
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crazywai1221
1 year ago
Selected Answer: D
the only answer is D, no other choice
upvoted 1 times
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csco10320953
1 year, 1 month ago
/30 -only 4 ip address. 192.168.1.0 to 192.168.1.4 - First network 192.168.1.5 to 192.168.1.8-Second network . Answer :D
upvoted 4 times
csco10320953
1 year, 1 month ago
192.168.1.0 to 192.168.1.3 -First network 192.168.1.4 to 192.168.1.7-Second network Answer:D
upvoted 2 times
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JohnRasher
1 year, 2 months ago
Selected Answer: D
Without going deep into network theory, here's the executive summary. The answer is D. Now, here's the explanation in networking terms. Host IP 192.168.1.3 belongs to subnet 192.168.1.0/30. Host IP 192.168.1.6 belongs to subnet 192.168.1.4/30. Therefore the hosts are in different subnets. In order for hosts to communicate across subnet boundaries, you must have a router. And all of this leaves out the issue of giving a host the IP of 192.168.1.3, which is the broadcast address of the first subnet. Can you do it? Yes, technically it's possible. It also creates a broadcast storm because that host endlessly replies to every broadcast packet on the subnet.
upvoted 5 times
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Dee83
1 year, 3 months ago
B. Since each computer is on the same layer 3 network, traffic between the computers may be processed by a network router in order to communicate. The IP/CIDR address of 192.168.1.3/30 and the IP/CIDR address of 192.168.1.6/30 are on the same network (192.168.1.0/30), because the network portion of the IP address (192.168.1) is the same and the subnet mask (30) indicates that only 2 addresses are available in the subnet. So the two computers are on the same layer 3 network and can communicate directly with each other without the need for a network bridge or router.
upvoted 1 times
luciusinf
1 year, 2 months ago
Bro, get your facts right. Network portion of the IP address is not 192.168.1 (that would be available for /24). In this case we have /30 which would make the network part 192.168.1.0000 00/. 192.168.1.3/30 has network 192.168.1.0 (192.168.1.0000 00/11) and 192.168.1.6/30 has network 192.168.1.4 (192.168.1.0000 01/10). If you don't know what i just said, you have no idea of the fundamentals of networking, subnetting. The answer is D.
upvoted 2 times
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oudmaster
1 year, 4 months ago
Selected Answer: D
D is the right answer. And 192.168.1.3/30 is a broadcast address, not valid IP address for a host. ! stupid ISC2 question as usual.
upvoted 1 times
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[Removed]
1 year, 6 months ago
Devices on different subnets require a L3 device to route traffic between the subnets.
upvoted 1 times
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OROR
1 year, 6 months ago
They are on the same network the traffic does not get to the router
upvoted 1 times
Jamati
1 year, 5 months ago
They are on different networks
upvoted 2 times
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jon1991
1 year, 7 months ago
Selected Answer: D
The answer is - D -
upvoted 6 times
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A (35%)
C (25%)
B (20%)
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