How to setup FTP proxying using the built in proxy code.

========================================================

NOTE: Currently, the built-in FTP proxy is only available for use with NAT

(i.e. only if you're already using "map" rules with ipnat). It does

support null-NAT mappings, that is, using the proxy without changing

the addresses.

Lets assume your network diagram looks something like this:

[host A]

|a

---+-------------+----------

|b

[host B]

|c

---+-------------+----------

|d

[host C]

and IP Filter is running on host B. If you want to proxy FTP from A to C

then you would do:

map int-c ipaddr-a/32 -> ip-addr-c-net/32 proxy port ftp ftp/tcp

int-c = name of "interface c"

ipaddr-a = ip# of interface a

ipaddr-c-net = another ip# on the C-network (usually not the same as the

interface).

e.g., if host A was 10.1.1.1, host B had two network interfaces ed0 and vx0

which had IP#'s 10.1.1.2 and 203.45.67.89 respectively, and host C was

203.45.67.90, you would do:

map vx0 10.1.1.1/32 -> 203.45.67.91/32 proxy port ftp ftp/tcp

where:

ipaddr-a = 10.1.1.1

int-c = vx0

ipaddr-c-net = 203.45.67.91

The "map" rule for this proxy should precede any other NAT rules you are

using.