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What routing issues appear when ACLs overlap across multiple interfaces?

Asked on Nov 23, 2025

Answer

Overlapping ACLs across multiple interfaces can lead to routing issues such as unintended traffic blocking, asymmetric routing, and increased complexity in troubleshooting. These problems arise when ACLs are not carefully designed, leading to conflicts in packet filtering and routing decisions.

Example Concept: Overlapping ACLs can cause routing issues by creating conflicting rules that affect packet forwarding. When ACLs on different interfaces have overlapping conditions, packets may be dropped or misrouted due to inconsistent rule application. This can lead to asymmetric routing, where return traffic takes a different path than the outgoing traffic, causing issues with stateful inspection or NAT. Properly organizing and documenting ACLs, and using tools like Cisco IOS or Juniper Junos to simulate and test ACL behavior, can help mitigate these issues.

Additional Comment:

Ensure ACLs are consistently applied across interfaces to prevent conflicts.
Regularly audit and document ACL rules to maintain clarity and prevent overlap.
Use network simulation tools to test ACL configurations before deployment.
Consider using centralized management tools for ACLs to streamline updates and changes.

✅ Answered with Networking best practices.

Ask any question about Networking here... and get an instant response.

What routing issues appear when ACLs overlap across multiple interfaces?

Asked on Nov 23, 2025

Answer

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