Some of my readers commented on my old article about reflexive access-list with issues in the configuration. I tried it in the lab again to be sure I didn’t make any mistake in the configuration example and here I’m sharing the lab and the config used.
About Reflexive Access Lists
Extended ACLs are a special kind of extended access-lists that have limited stateful behaviour technique implemented for TCP sessions. It is better to say that reflexive access-list is simulating stateful behaviour because it, by use of ‘established’ command, is allowing TCP packets that have the ‘ACK’ bit set but not the initial ‘SYN-only’ packet. In this way, we are effectively permitting only the packets that are part of an established session.
In my prior article, I showed how this works by enabling PING from PC1 in VLAN 10 to PC2 in VLAN 20 but not the other way.
I created the lab topology in GNS3: