ASA same-security-traffic permit inter-interface vs ACL

[alexandru.cacean]

Hi all.

I have ASA 5525 with subinterfaces for internal VLANs and one interface is connected to ISP and is NAT'ing internal networks with dynamic NAT. Also I have global ACL's which permit traffic between a part of vlans and deny traffic between another VLANs. Another option which is set on ASA is "same-security-traffic permit inter-interface". In this case it seems that all is working good. But if I disable "same-security-traffic permit inter-interface" the traffic between internal subinterfaces (with the same security level) is not passing although an explicit ACL which permit traffic between these interfaces is configured in global.

I was not able to find the documentation about ACL vs "same-security-traffic permit inter-interface", could somebody tell me - does

"same-security-traffic permit inter-interface" have precedence over explicit ACL ?

[Karsten Iwen]

In the old days of the PIX it was a feature. If two interfaces have the same security-level, then they are separated and can't communicate with each other regardless what else is configured. Later when the FWSM was introduced it was possible to have Firewalls with more then 101 interfaces. A feature was needed to overwrite this functionality.  This behavior is still valid, but of course we can disable this function with the mentioned command. So yes, the command has precedence over an ACL.

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[alexandru.cacean]

thank you, but can you give me an link to detailed documentation ?

[Karsten Iwen · Accepted solution]

nothing more then what is in the official documentation:

http://www.cisco.com/en/US/docs/security/asa/asa91/configuration/general/interface_complete_routed.html#wp1325183

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Don't stop after you've improved your network! Improve the world by lending money to the working poor:
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[alexandru.cacean]

thank you very much