ASA - same-security-traffic command

Α Cisco ASA will use rules pertaining to the security levels configured on particular interfaces to allow or disallow traffic flow by default. Even if two interfaces have the same security level, traffic is disallowed.

However, this behavior can be modified using the same-security-traffic command. For example, the following command will allow traffic to flow from one interface to another, even if they have the same security level:

ASA#configure terminal  
ASA(config)#same-security-traffic permit inter-interface

Similarly, the following command will allow traffic to flow to and from the same interface.

ASA#configure terminal  
ASA(config)#same-security-traffic permit intra-interface

Links:

https://forum.networklessons.com/t/cisco-asa-security-levels/812/46?u=lagapidis

https://networklessons.com/cisco/asa-firewall/cisco-asa-security-levels/

https://www.cisco.com/en/US/docs/security/asa/asa81/command/reference/s1.html#wp1346877