What happens if a packet does not match any entries in an ACL?
Understand the Problem
The question is asking about the behavior of a packet when it does not match any entries in an Access Control List (ACL) in a networking context. It is seeking to clarify the resulting action taken on the packet according to network security protocols.
Answer
The packet is denied by an implicit deny rule.
If a packet does not match any entries in an ACL, the packet is denied by an implicit deny rule.
Answer for screen readers
If a packet does not match any entries in an ACL, the packet is denied by an implicit deny rule.
More Information
In many networking devices, such as routers and switches, all access control lists (ACLs) end with an implicit 'deny all' rule. This means if a packet does not match any specified rules in the ACL, it is automatically denied, ensuring security by default.
Tips
A common mistake is assuming that there is no default action if no match is found; however, the implicit deny ensures unmatched packets are not allowed, ensuring security configurations are not bypassed.
Sources
- HP Networking - ACL configuration - support.hpe.com
- Cisco CCNA - Access Lists Defined - certificationkits.com
- Purpose of ACLs (4.1) > ACL Concepts | Cisco Press - ciscopress.com
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