I have a question regarding the behaviour of the ASA with respect to the 'telnet X.X.X.X Y.Y.Y.Y interface' command.
If I am connected to the inside interface, and the ASA is configured to allow telnet to the inside interface from my IP address, and I try to connect to the outside interface, the TCP handshake completes, but the connection is then reset by the ASA.
If I am connected to the inside interface, and the ASA is configured to NOT allow telnet to the inside interface from my IP address, and I try to connect to the inside interface, the TCP handshake doesn't complete - the ASA doesn't respond to any of my SYN packets.
Can anyone explain why it responds differently under these two conditions?
The only explanation I can think of is that the in step 2, the ASA creates a dynamic ACL entry permitting some telnet traffic but more importantly, denying other telnet traffic to the interface, therefore the packet is dropped at laye3/4.
In step 1, the telnet traffic is not destined for the inside interface so passes through the inside interface by default. the 'telnet X.X.X.X Y.Y.Y.Y interface' restricts access to the ASA's telnet server process, which is at layer 7, which is why the layer 3/4 part of it completes.
Can anyone else explain this behaviur and also am I correct that the 'telnet X.X.X.X Y.Y.Y.Y interface' command creates a dynamic ACL entry on the specified interface?
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...