configuring ftp help

What's weird is that it works internally but does not work from outside(internet).what does internal mean? is it in internal (server) vlan?

this is mine. ftp client ip is 172.28.19.251. it is in external vlan.

[root@ve1023:Active] config  b virtual bar list
virtual bar {
   snat automap
   pool foo
   destination 172.28.19.79:21
   ip protocol 6
   profiles {
      ftp {}
      tcp {}
   }
}
[root@ve1023:Active] config  b pool foo list
pool foo {
   members 200.200.200.101:21 {}
}

1 active mode ftp

[root@centos251 tmp] ncftp 172.28.19.79
NcFTP 3.2.0 (Aug 05, 2006) by Mike Gleason (http://www.NcFTP.com/contact/).
Connecting to 172.28.19.79...
(vsFTPd 2.0.5)
Logging in...
Login successful.
Logged in to 172.28.19.79.
ncftp / > set passive off
ncftp / > cd pub
Directory successfully changed.
ncftp /pub > ls -l
-rw-r--r--    1 0        0   1012865024   Apr  6  2012   BIGIP-11.1.0.1943.0.iso
ncftp /pub > get BIGIP-11.1.0.1943.0.iso
BIGIP-11.1.0.1943.0.iso:                               965.94 MB   22.09 MB/s

[root@ve1023:Active] config  b conn show all
VIRTUAL 172.28.19.79:21 <-> NODE 200.200.200.101:21   TYPE any   1/0
    CLIENTSIDE 172.28.19.251:33027 <-> 172.28.19.79:21
        (pkts,bits) in = (30, 1870)   out = (21, 2001)
    SERVERSIDE 200.200.200.10:33027 <-> 200.200.200.101:21
        (pkts,bits) in = (27, 2309)   out = (26, 1668)
    PROTOCOL 6   UNIT 1   IDLE 0 (300)   LASTHOP external 00:50:56:b3:03:8f
VIRTUAL 172.28.19.79:21 <-> NODE 172.28.19.251:43590   TYPE any   1/0
    CLIENTSIDE 200.200.200.101:20 <-> 200.200.200.10:43590
        (pkts,bits) in = (113361, 169.4M)   out = (10740, 575012)
    SERVERSIDE 172.28.19.79:20 <-> 172.28.19.251:43590
        (pkts,bits) in = (10740, 575012)   out = (113361, 169.4M)
    PROTOCOL 6   UNIT 1   IDLE 0 (300)   LASTHOP internal 00:50:56:b3:01:0b

2 passive mode ftp

[root@centos251 tmp] ncftp 172.28.19.79
NcFTP 3.2.0 (Aug 05, 2006) by Mike Gleason (http://www.NcFTP.com/contact/).
Connecting to 172.28.19.79...
(vsFTPd 2.0.5)
Logging in...
Login successful.
Logged in to 172.28.19.79.
ncftp / > set passive on
ncftp / > cd pub
Directory successfully changed.
ncftp /pub > get BIGIP-11.1.0.1943.0.iso
BIGIP-11.1.0.1943.0.iso:                               965.94 MB   18.07 MB/s

[root@ve1023:Active] config  b conn show all
VIRTUAL 172.28.19.79:21 <-> NODE 200.200.200.101:21   TYPE any   1/0
    CLIENTSIDE 172.28.19.251:33028 <-> 172.28.19.79:21
        (pkts,bits) in = (24, 1487)   out = (17, 1632)
    SERVERSIDE 200.200.200.10:33028 <-> 200.200.200.101:21
        (pkts,bits) in = (23, 1943)   out = (22, 1387)
    PROTOCOL 6   UNIT 1   IDLE 0 (300)   LASTHOP external 00:50:56:b3:03:8f
VIRTUAL 172.28.19.79:6925 <-> NODE 200.200.200.101:6925   TYPE any   1/0
    CLIENTSIDE 172.28.19.251:42992 <-> 172.28.19.79:6925
        (pkts,bits) in = (46521, 2.499M)   out = (489847, 731.8M)
    SERVERSIDE 200.200.200.10:42992 <-> 200.200.200.101:6925
        (pkts,bits) in = (489847, 731.8M)   out = (46521, 2.499M)
    PROTOCOL 6   UNIT 1   IDLE 0 (300)   LASTHOP external 00:50:56:b3:03:8f