Question 1mediummultiple choice
Full question →An ACL entry reads:
access-list 25 permit 192.168.8.0 0.0.0.15
Which address range does this statement match?
mediummultiple choiceObjective-mapped
An ACL entry reads:
access-list 25 permit 192.168.8.0 0.0.0.15
Which address range does this statement match?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
192.168.8.0 through 192.168.8.15
That is the correct range for a wildcard of 0.0.0.15.
B
Distractor review
192.168.8.0 through 192.168.8.31
That would match a wildcard of 0.0.0.31.
C
Distractor review
192.168.8.8 through 192.168.8.15
The range starts at .0, not .8.
D
Distractor review
Only host 192.168.8.15
A host match would use a wildcard of 0.0.0.0.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is mistaking the wildcard mask for a subnet mask or miscalculating the starting IP address of the range. Many candidates incorrectly assume the range starts at 192.168.8.8 or that the wildcard mask 0.0.0.15 matches 32 addresses instead of 16. This happens because the wildcard mask is the inverse of a subnet mask and controls which bits can vary. If the base IP address is not aligned to the block size defined by the wildcard mask, the ACL will not match the intended range. Understanding that the base address must be a multiple of the block size (16 in this case) helps avoid this pitfall.
Technical deep dive
How to think about this question
Access Control Lists (ACLs) in Cisco networking use wildcard masks to specify which IP addresses to match in a rule. A wildcard mask is the inverse of a subnet mask, where a 0 bit means "match exactly" and a 1 bit means "ignore this bit". In the ACL entry "access-list 25 permit 192.168.8.0 0.0.0.15", the wildcard mask 0.0.0.15 allows variation in the last 4 bits of the IP address, effectively matching a block of 16 addresses starting from 192.168.8.0. The rule for determining the address range matched by an ACL entry is to add one to the wildcard mask value plus the base IP address. Since 0.0.0.15 corresponds to binary 00001111, it means the last 4 bits can vary from 0000 to 1111 (0 to 15 decimal). Therefore, the ACL matches all IP addresses from 192.168.8.0 through 192.168.8.15 inclusive. This is a common technique in ACLs to efficiently permit or deny a small subnet or range of hosts. A common exam trap is confusing wildcard masks with subnet masks or misinterpreting the starting address of the range. For example, assuming the range starts at 192.168.8.8 instead of 192.168.8.0 is incorrect because the base address must align with the wildcard mask block size. Practically, Cisco routers use this wildcard mask logic to quickly filter traffic based on IP ranges, making understanding this concept critical for ACL configuration and troubleshooting.
KKey Concepts to Remember
- An ACL wildcard mask uses 0 bits to require an exact match and 1 bits to allow any value in that bit position.
- The wildcard mask 0.0.0.15 allows variation in the last 4 bits of the IP address, matching a block of 16 addresses.
- The base IP address in an ACL entry must align with the wildcard mask block size to correctly define the address range.
- ACLs use wildcard masks to efficiently permit or deny traffic from specific IP address ranges in Cisco routers.
- Misinterpreting wildcard masks as subnet masks leads to incorrect address range calculations in ACL configurations.
- The address range matched by an ACL entry is from the base IP address up to base plus the wildcard mask value.
- Cisco ACLs process entries sequentially, so precise wildcard mask usage ensures correct traffic filtering behavior.
- Understanding wildcard masks is essential for configuring and troubleshooting ACLs in the CCNA Security Fundamentals domain.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
An ACL wildcard mask uses 0 bits to require an exact match and 1 bits to allow any value in that bit position.
What is the correct answer to this question?
The correct answer is: 192.168.8.0 through 192.168.8.15 — A wildcard of 0.0.0.15 means the last 4 bits can vary, which corresponds to a block size of 16 addresses. Starting at 192.168.8.0, the range is 192.168.8.0 through 192.168.8.15.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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