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Astron
Asked: 2012-01-10 20:18:55 +0800 CST

Cisco ASA 8.4 port forwarding

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I am having trouble port-forwarding on an Cisco ASA from a host on the internet to a host on the internal network. The outside interface of the ASA is assigned via DHCP. Is there something else that has to be done in order to make this work correctly?

update to problem

(outside) to (outside) source dynamic VPN_NETWORK interface

per:

https://www.cisco.com/en/US/docs/security/asa/asa84/configuration/guide/nat_rules.html

(outside) to (outside) after-auto source dynamic VPN_NETWORK interface

packet-tracer:

# packet-tracer input outside tcp 74.x.x.x 1025 71.x.x.x 555

Phase: 1
Type: ROUTE-LOOKUP
Subtype: input
Result: ALLOW
Config:
Additional Information:
in   71.x.x.x    255.255.255.255 identity

Phase: 2
Type: ACCESS-LIST
Subtype:
Result: DROP
Config:
Implicit Rule
Additional Information:

Result:
input-interface: outside
input-status: up
input-line-status: up
output-interface: NP Identity Ifc
output-status: up
output-line-status: up
Action: drop
Drop-reason: (acl-drop) Flow is denied by configured rule

running-config

ASA Version 8.4(2) 
!
hostname asa
enable password ***** encrypted
passwd ***** encrypted
names
!
interface Ethernet0/0
 switchport access vlan 2
!
interface Ethernet0/1
!
interface Ethernet0/2
!
interface Ethernet0/3
!
interface Ethernet0/4
!
interface Ethernet0/5
!
interface Ethernet0/6
!
interface Ethernet0/7
!
interface Vlan1
 nameif inside
 security-level 100
 ip address 172.16.1.1 255.255.255.0 
!
interface Vlan2
 nameif outside
 security-level 0
 ip address dhcp setroute 
!
boot system disk0:/asa842-k8.bin
ftp mode passive
same-security-traffic permit intra-interface
object network obj_any
 subnet 0.0.0.0 0.0.0.0
object network VPN_NETWORK
 subnet 192.168.1.0 255.255.255.192
object network VM
 host 172.16.1.100
access-list dynamic-filter_acl extended permit ip any any 
access-list VM-IN extended permit tcp any host 172.16.1.100 eq 555 
pager lines 24
logging enable
logging asdm informational
mtu inside 1500
mtu outside 1500
ip local pool VPN-DHCP-POOL 192.168.1.10-192.168.1.50
icmp unreachable rate-limit 1 burst-size 1
asdm image disk0:/asdm-645-206.bin
no asdm history enable
arp timeout 14400
nat (inside,outside) source static any any destination static VPN_NETWORK VPN_NETWORK no-proxy-arp route-lookup
nat (outside,outside) source dynamic VPN_NETWORK interface
!
object network obj_any
 nat (inside,outside) dynamic interface
object network VM
 nat (inside,outside) static interface service tcp 555 555 
access-group VM-IN in interface outside
timeout xlate 3:00:00
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 http console LOCAL 
aaa authentication ssh console LOCAL 
http server enable
http 172.16.1.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
crypto ipsec ikev1 transform-set ESP-AES-256-SHA esp-aes-256 esp-sha-hmac 
crypto ipsec ikev1 transform-set ESP-AES-128-SHA esp-aes esp-sha-hmac 
crypto ipsec ikev1 transform-set ESP-AES-192-SHA esp-aes-192 esp-sha-hmac 
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set pfs group1
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set ikev1 transform-set ESP-AES-256-SHA
crypto map outside_map 65535 ipsec-isakmp dynamic SYSTEM_DEFAULT_CRYPTO_MAP
crypto map outside_map interface outside
crypto map inside_map 65535 ipsec-isakmp dynamic SYSTEM_DEFAULT_CRYPTO_MAP
crypto map inside_map interface inside
crypto ikev1 enable inside
crypto ikev1 enable outside
crypto ikev1 policy 10
 authentication crack
 encryption aes-256
 hash sha
 group 2
 lifetime 86400
crypto ikev1 policy 20
 authentication rsa-sig
 encryption aes-256
 hash sha
 group 2
 lifetime 86400
crypto ikev1 policy 30
 authentication pre-share
 encryption aes-256
 hash sha
 group 2
 lifetime 86400
telnet timeout 5
ssh 172.16.1.0 255.255.255.0 inside
ssh timeout 5
ssh version 2
console timeout 0

dhcp-client client-id interface outside
dhcpd auto_config outside
!
dhcpd address 172.16.1.100-172.16.1.200 inside
dhcpd dns 8.8.8.8 8.8.4.4 interface inside
dhcpd option 3 ip 172.16.1.1 interface inside
dhcpd enable inside
!
threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
dynamic-filter enable interface outside classify-list dynamic-filter_acl
dynamic-filter drop blacklist interface outside 
ssl encryption des-sha1
webvpn
group-policy EdgeAccess internal
group-policy EdgeAccess attributes
 dns-server value 8.8.8.8 8.8.4.4
 vpn-tunnel-protocol ikev1 
username user password ***** encrypted
tunnel-group EdgeAccess type remote-access
tunnel-group EdgeAccess general-attributes
 address-pool VPN-DHCP-POOL
 default-group-policy EdgeAccess
tunnel-group EdgeAccess ipsec-attributes
 ikev1 pre-shared-key *****
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map type inspect dns preset_dns_map
 parameters
  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
privilege show level 0 mode configure command filter
privilege cmd level 0 mode configure command filter
privilege cmd level 0 mode config-group-webvpn command filter
privilege cmd level 0 mode config-username-webvpn command filter
prompt hostname context 
no call-home reporting anonymous
: end
cisco nat port-forwarding access-control-list cisco-asa

1 Answers

  1. Best Answer

    As of version 8.3, access lists applied with an access-group statement always use the real IP address, even if the incoming packet is directed at a NAT'd IP; see the ASA Version 8.3 Migration Guide for details.

    Your access list should instead look like this:

    access-list VM_IN extended permit tcp any host 172.16.1.125 eq 777

    Or, even better, use the object so you only have to update it in one place in the future:

    access-list VM_IN extended permit tcp any object VM eq 777

    EDIT (reflecting clarification from Astron):

    To do inbound port forwarding to an internal host 192.168.1.125 on an interface that has a dynamically-assigned address (e.g. DHCP):

    object network VM
 host 192.168.1.125
!
object network VM
 nat (inside,outside) static interface service tcp 777 777
!
access-list VM_IN extended permit tcp any object VM eq 777
!
access-group VM_IN in interface outside

    The key is the static interface part in the nat statement. It will replace interface with whatever the IP of the outside interface happens to be at the time a packet arrives for translation.

    • 6