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I need help to resolve this issue. I have a Cisco ASA 5512 and I’m trying to access to my FTP server from external IP but the packets are dropped. Please find the network diagram below:

enter image description here

I typed this commands:

object network FTPServer
 host 10.3.3.128
 nat (Inside,Outside) static interface service tcp 21 21
access-list Outside_access_in extended permit tcp any object FTPServer eq ftp

The packets are dropped by NAT rule, here’s the packet-tracer result:

packet-tracer input outside tcp 193.252.204.12 12345 10.3.3.128 21

Phase: 1
Type: ROUTE-LOOKUP
Subtype: input
Result: ALLOW
Config:
Additional Information:
in   10.3.3.0        255.255.255.0   Inside

Phase: 2
Type: ACCESS-LIST
Subtype: log
Result: ALLOW
Config:
access-group Outside_access_in in interface Outside
access-list Outside_access_in extended permit tcp any object FTPServer eq ftp
Additional Information:

Phase: 3
Type: NAT
Subtype: per-session
Result: ALLOW
Config:
Additional Information:

Phase: 4
Type: IP-OPTIONS
Subtype:
Result: ALLOW
Config:
Additional Information:

Phase: 5
Type: INSPECT
Subtype: inspect-ftp
Result: ALLOW
Config:
class-map inspection_default
 match default-inspection-traffic
policy-map global_policy
 class inspection_default
  inspect ftp
service-policy global_policy global
Additional Information:

Phase: 6
Type: NAT
Subtype: rpf-check
Result: DROP
Config:
object network FTPServer
 nat (Inside,Outside) static interface service tcp ftp ftp
Additional Information:

Result:
input-interface: Outside
input-status: up
input-line-status: up
output-interface: Inside
output-status: up
output-line-status: up
Action: drop
Drop-reason: (acl-drop) Flow is denied by configured rule

Please find the full configuration below:

ASA Version 9.1(2)
!
hostname ASA
names
ip local pool PoolVPN 192.168.33.100-192.168.33.150 mask 255.255.255.0
!
interface GigabitEthernet0/0
 nameif Outside
 security-level 0
 ip address 62.X.X.226 255.255.255.248
!
interface GigabitEthernet0/1
 nameif Inside
 security-level 100
 ip address 10.3.3.48 255.255.255.0
!
interface GigabitEthernet0/2
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet0/3
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet0/4
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet0/5
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Management0/0
 management-only
 nameif management
 security-level 100
 ip address 192.168.1.1 255.255.255.0
!
ftp mode passive
object network LanLOCAL
 subnet 10.3.3.0 255.255.255.0
object network PoolVPN
 subnet 192.168.33.0 255.255.255.0
object network FTPServer
 host 10.3.3.128
access-list Inside_access_out extended permit ip 10.3.3.0 255.255.255.0 object PoolVPN log disable
access-list Outside_access_in extended permit tcp any object FTPServer eq ftp
pager lines 24
logging enable
logging asdm informational
mtu Outside 1500
mtu Inside 1500
mtu management 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
no asdm history enable
arp timeout 14400
no arp permit-nonconnected
nat (Inside,Outside) source static any any destination static PoolVPN PoolVPN no-proxy-arp route-lookup
!
object network FTPServer
 nat (Inside,Outside) static interface service tcp ftp ftp
!
nat (Inside,Outside) after-auto source dynamic LanLOCAL interface
access-group Outside_access_in in interface Outside
route Outside 0.0.0.0 0.0.0.0 62.X.X.225 1
route Inside 10.0.0.0 255.0.0.0 10.3.3.250 1
timeout xlate 3:00:00
timeout pat-xlate 0:00:30
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
timeout floating-conn 0:00:00
dynamic-access-policy-record DfltAccessPolicy
user-identity default-domain LOCAL
aaa authentication ssh console LOCAL
http server enable
http 192.168.1.0 255.255.255.0 management
http 10.0.0.0 255.0.0.0 Inside
no snmp-server location
no snmp-server contact
crypto ipsec security-association pmtu-aging infinite
crypto ca trustpoint _SmartCallHome_ServerCA
 no validation-usage
 crl configure
crypto ca trustpool policy

telnet timeout 5
ssh 10.0.0.0 255.0.0.0 Inside
ssh timeout 5
ssh key-exchange group dh-group1-sha1
console timeout 0
dhcpd address 192.168.1.2-192.168.1.254 management
dhcpd enable management
!
threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
webvpn
 enable Outside
 anyconnect image disk0:/anyconnect-win-2.5.2014-k9.pkg 1
 anyconnect image disk0:/anyconnect-macosx-i386-2.5.2014-k9.pkg 2
 anyconnect enable
 tunnel-group-list enable
 cache
  disable
 error-recovery disable
group-policy GroupPolicy_VPN-Test internal
group-policy GroupPolicy_VPN-Test attributes
 wins-server none
 dns-server value 10.3.3.5
 vpn-tunnel-protocol ssl-client
 default-domain value TEST.local
tunnel-group VPN-Test type remote-access
tunnel-group VPN-Test general-attributes
 address-pool PoolVPN
 default-group-policy GroupPolicy_VPN-Test
tunnel-group VPN-Test webvpn-attributes
 group-alias VPN-Test enable
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map type inspect dns preset_dns_map
 parameters
  message-length maximum client auto
  message-length maximum 512
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect rsh
  inspect rtsp
  inspect esmtp
  inspect sqlnet
  inspect skinny
  inspect sunrpc
  inspect xdmcp
  inspect sip
  inspect netbios
  inspect tftp
  inspect ip-options
!
service-policy global_policy global
prompt hostname context
call-home reporting anonymous
Cryptochecksum:72ad3302b53c0add5a8574806a963e27
: end

Can anyone help me?

  • What about the FTP data port (20)? – Ron Maupin Sep 18 '17 at 11:47
5
  1. The IP address of FTP Server you used in packet-tracer input outside tcp 193.252.204.12 12345 10.3.3.128 21 is NOT correct, you should use 62.X.X.226.

    Therefore, your correct packet-tracer command is as below:

    packet-tracer input outside tcp 193.252.204.12 12345 62.X.X.226 21

  2. You may need another similar object, rule and NAT statement for FTP Data Port 20 if it still does not work.

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