![]() ![]() With the use of the state table in addition to administrator-defined rules, filtering decisions are based on context that is established by packets previously passed through the firewall. The firewall, through stateful inspection, also monitors the state of the connection to compile information to place in a state table. Through the stateful application inspection used by the Adaptive Security Algorithm, the Security Appliance tracks each connection that traverses the firewall and ensures that they are valid. The Security Appliance supports application inspection through the Adaptive Security Algorithm function. Refer to the Cisco Technical Tips Conventions for more information on document conventions. This configuration can also be used with Cisco Adaptive Security Appliance 8.3 and later. They are RFC 1918 addresses which have been used in a lab environment. Note: The IP addressing schemes used in this configuration are not legally routable on the Internet. If your network is live, make sure that you understand the potential impact of any command. All of the devices used in this document started with a cleared (default) configuration. The information in this document was created from the devices in a specific lab environment. Windows 2003 Server that runs TFTP servicesĬlient PC located on the outside of the network Windows 2003 Server that runs FTP services The information in this document is based on these software and hardware versions:ĪSA 5500 Series Adaptive Security Appliance that runs the 8.4(1) software image You have a configured the FTP server located in your DMZ network. There is basic communication between required interfaces. Prerequisites RequirementsĮnsure that you meet these requirements before you attempt this configuration: TFTP, as described in RFC 1350, is a simple protocol to read and write files between a TFTP server and client. Refer to PIX/ASA 7.x: Enable FTP/TFTP Services Configuration Example for the same configuration on Cisco Adaptive Security Appliance (ASA) with versions 8.2 and earlier. Also, users outside headed inbound to your FTP server are denied access. Without the inspection command configuration on the Security Appliance, FTP from inside users headed outbound works only in Passive mode. The client then initiates the connection from port N+1 to port P on the server to transfer data. The result of this is that the server then opens a random unprivileged port (P>1023) and sends the port P command back to the client. But instead of then issuing a port command and allowing the server to connect back to its data port, the client issues the PASV command. ![]() The first port contacts the server on port 21. When an FTP connection is opened, the client opens two random unprivileged ports locally (N>1023 and N+1). In Passive FTP mode, the client initiates both connections to the server, which solves the problem of a firewall that filters the incoming data port connection to the client from the server. The server then connects back to the specified data ports of the client from its local data port, which is port 20. Then the client starts to listen to port N+1 and sends the FTP command port N+1 to the FTP server. In Active FTP mode, the client connects from a random unprivileged port (N>1023) to the command port (21) of the FTP server. This document explains the steps required for users outside of your network to access FTP and TFTP services in your DMZ network.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |