The answer is that all traffic from the 10.0.0.0/8 network is permitted inbound on GigabitEthernet0/0. This is correct because the wildcard mask 0.255.255.255 tells the ACL to match the first octet exactly (10) while ignoring the remaining three octets, effectively permitting any source IP from 10.0.0.0 through 10.255.255.255. On the Cisco CCNP ENARSI 300-410 exam, this tests your ability to interpret ACL wildcard masks, specifically how a mask of 0.255.255.255 is the inverse of a /8 subnet mask (255.0.0.0). A common trap is confusing wildcard masks with subnet masks—remember that wildcard bits of 0 mean "must match exactly," while bits of 1 mean "ignore." Here, the 0 in the first octet forces an exact match on 10, and the 255s in the last three octets mean "any value." A quick memory tip: think of the wildcard mask as "0 = check, 255 = don't check," so 0.255.255.255 checks only the first octet.
300-410 IPv4 Access Control Lists Practice Question
This 300-410 practice question tests your understanding of ipv4 access control lists. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Consider this configuration on router R2:
```
interface GigabitEthernet0/0
ip access-group RESTRICT_ACCESS in
!
ip access-list extended RESTRICT_ACCESS
permit ip 10.0.0.0 0.255.255.255 any
deny ip any any
```
What traffic will be permitted inbound on GigabitEthernet0/0?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
All traffic from the 10.0.0.0/8 network.
The access list RESTRICT_ACCESS uses a wildcard mask of 0.255.255.255, which matches the first octet exactly and ignores the remaining three octets. This effectively permits all traffic from the 10.0.0.0/8 network (10.0.0.0 through 10.255.255.255). The explicit deny ip any any at the end blocks all other traffic, so only traffic sourced from the 10.0.0.0/8 range is permitted inbound on GigabitEthernet0/0.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Only traffic from source 10.0.0.0/24.
Why it's wrong here
Incorrect. The wildcard mask 0.255.255.255 matches all addresses starting with 10, not just 10.0.0.0/24.
✓
All traffic from the 10.0.0.0/8 network.
Why this is correct
Correct. The wildcard mask 0.255.255.255 matches the 10.0.0.0/8 range.
Related concept
Read the scenario before looking for a memorised answer.
✗
All traffic from any source.
Why it's wrong here
Incorrect. The explicit deny statement blocks all traffic not matching the permit.
✗
Only traffic from source 10.0.0.0/16.
Why it's wrong here
Incorrect. The wildcard mask 0.255.255.255 matches /8, not /16.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between prefix length and wildcard mask, leading candidates to misinterpret 0.255.255.255 as a /24 or /16 mask instead of the correct /8 range.
Detailed technical explanation
How to think about this question
In Cisco ACLs, the wildcard mask uses 0 to mean 'must match' and 1 to mean 'ignore'. The mask 0.255.255.255 means the first octet (10) must match exactly, while the remaining three octets are wildcarded, yielding a network range of 10.0.0.0/8. This is a common way to permit all RFC 1918 Class A private addresses. A real-world scenario is restricting management access to a router to only internal 10.x.x.x hosts while blocking all other sources.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
IPv4 Access Control Lists — This question tests IPv4 Access Control Lists — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: All traffic from the 10.0.0.0/8 network. — The access list RESTRICT_ACCESS uses a wildcard mask of 0.255.255.255, which matches the first octet exactly and ignores the remaining three octets. This effectively permits all traffic from the 10.0.0.0/8 network (10.0.0.0 through 10.255.255.255). The explicit deny ip any any at the end blocks all other traffic, so only traffic sourced from the 10.0.0.0/8 range is permitted inbound on GigabitEthernet0/0.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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