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Zorluk: KolayFirewalls and Access Control Lists (ACLs)

A network technician is configuring an Access Control List (ACL) on a router interface to allow web traffic to an internal web server at 192.168.1.50 via HTTPS (TCP port 443). The technician adds an explicit rule permitting this traffic. However, after applying the ACL, all other network traffic passing through the interface is immediately blocked, despite no explicit deny rules being added to the configuration. Which fundamental ACL feature causes this automatic blocking behavior?

  1. Implicit denyCevap
  2. B
    Port address translation (PAT) overload
  3. C
    OSI Layer 2 frame encapsulation
  4. D
    UDP connectionless session tracking

Cevap

The implicit deny feature causes this behavior, as firewalls and ACLs automatically append an unwritten rule at the end of every rule list that drops all unmatched traffic.
The implicit deny feature is a standard security default in network ACLs and firewalls. Once an ACL is active on an interface, any packet that fails to match any explicit permit statement is automatically dropped by the implicit deny rule at the end of the evaluation list.

Adım Adım Çözüm

1
Analyze the observed issue after applying the ACL.
Traffic not explicitly matched by the permit rule is blocked automatically.
Network ACLs process packets sequentially from top to bottom until a match is found.
2
Identify the default catch-all mechanism at the end of an ACL.
The final implied statement is 'deny all traffic'.
This implicit deny rule ensures a default-deny security posture by dropping any traffic that was not explicitly permitted.

Anahtar Kavram

ACL Implicit Deny Feature
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Konular

Firewalls and Access Control Lists (ACLs)

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