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ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?

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ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?

This thread has been locked for further replies. You can start a new thread to share your ideas or ask questions.
ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?
ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?
2025-02-25 00:10:32 - last edited 2025-02-25 02:09:41
Model: SG2016P  
Hardware Version: V1
Firmware Version: 1.20.5

I have two "Interface" networks set up:

  • "Core" for the network devices and home computers
  • "Outer Core" for my wireless printer


Everything is successfully connected with IPs that show that they are in the correct subnets.  I can ping the printer from my desktop.

Now I'm trying to create an ACL so that the printer cannot touch the Core devices.

The ACL has the following properties:

  • Policy: Deny
  • Protocols: All
  • Rule:
    • Source: Network "Outer Core"
    • Destination: Network "Core"
  • ACL Binding (can't change these):
    • Binding type: Ports
    • Ports: All ports
  • Advanced settings:
    • Time Range: not enabled
    • Ethertype: not enabled

 

That's it.  When I create that rule, I can no longer even ping the printer that's in "Outer Core" from my desktop that's in "Core".  Disable the rule, wait a few seconds and I can ping again.

Not sure what I'm doing wrong.  Thoughts?



 

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Re:ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?-Solution
2025-02-25 02:09:28 - last edited 2025-02-25 02:09:41

Hi @DrNeau 

Thanks for posting in our business forum.

Understand how communication works.

Successful communication is bidirectional. Not unidirectional.

A > B and B > A. Good.

A > B good, B > A no good = bad communication.

 

And second concept, switch ACL is not stateful. Stateful and stateless has been explained in the guide on the router page. You can search and read it.

 

A > B, ACL block, B > A ACL allow = A > B works, B > A does not work, this is stateful ACL.

 

In SW ACL, you block A > B, with this single rule, A > B or B > A are both blocked.

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Re:ACL rule blocking traffic from "A" to "B" is also preventing communication from "B" into "A"?-Solution
2025-02-25 02:09:28 - last edited 2025-02-25 02:09:41

Hi @DrNeau 

Thanks for posting in our business forum.

Understand how communication works.

Successful communication is bidirectional. Not unidirectional.

A > B and B > A. Good.

A > B good, B > A no good = bad communication.

 

And second concept, switch ACL is not stateful. Stateful and stateless has been explained in the guide on the router page. You can search and read it.

 

A > B, ACL block, B > A ACL allow = A > B works, B > A does not work, this is stateful ACL.

 

In SW ACL, you block A > B, with this single rule, A > B or B > A are both blocked.

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