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New Member

FTP communication

I have a 2621 configured with the serial interface to the outside world, ethernet 0/0 to DMZ2, ethernet 0/1 to DMZ1, and using ios firewall. When I am connected to DMZ2 I can make FTP communications to the outside world uploading and downloading. When connected to the DMZ1 I am only able to download from the same FTP site. When attempting to upload I get an "Access Denied" message. It appears that the data channel can't be created.

I'm aware of the fixup protocol command but that isn't available on this router. How can I make this work and why does it work on one DMZ but not the other?

Thanks.

2 REPLIES
New Member

Re: FTP communication

Hi,

I guess your ftp mode is active because in this mode the client initiate connection to ftp server port 21 (command port) then the server initiate a connection to the client from ftp server source port 20 (data port).

In your case the connection to the port 21 is inspected by your inbound inspect ? default ? and will allow only responses to the connection initiated from the outside so connection attempts from the port 20 will be denied.

I hope this will help you!

New Member

Re: FTP communication

Hello.

The command "ip inspect name Default ftp" is equivalent to "fixup ftp". (nearly)

Solution (i believe) for your connection-problem:

1. Remove "ip inspect Default in" on interface FastEthernet0/0 and on interface FastEthernet0/1 (inside).

2. Add "ip inspect Default out" on interface Serial0/0 (outside).

3. Remove any permit-statement in access-list 120 for connections which are established from "inside" to outside (statefull expection! -> allow answers for questions from inside)

Or find connection-errors with

"debug ip inspect ..."

"debug ip nat ..."

And use route-maps:

"ip nat inside source route-map ..." because you use vpn (crypto map ...) -> use "acl-nonat access-lists"

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