ASA 8.3 - DMZ and inside connected to a server with 2 NIC?

gdi · ‎09-10-2010

We have an ASA5505 firewall, and 1 server on our internal network - this server runs DNS, mail, DHCP etc...

We want mail and webmail from external IPs to forwarded to our internal server.

We understand it is possible (but not easy) to do the port forwarding with NAT, access_rules etc... - I have spent way too much time trying to figure this out for ASA version 8.3(1) - big PITA!

The public server feature seems to be what we want, but it only works with DMZ (we currently do not use a DMZ as we have only 1 server).

Our internal server has 2 NIC cards (currently setup in parallel to increase bandwidth). Would it be possible/advisable to have 2 LAN connections from the ASA - a DMZ going directly to the server NIC1, and a normal connection to the rest of the LAN (and accessed by NIC2 on the server)?

All help appreciated!

mirober2 · ‎09-10-2010

Hello,

You can use Object NAT and an access-list to accomplish this with a couple of lines--no need to multi-home the server:

object network obj-server
    host 
    nat (inside,outside) static 
!
access-list outside_access_in permit tcp any host  eq 443
access-list outside_access_in permit tcp any host  eq 25
access-group outside_access_in in interface outside

That should do the trick for webmail and SMTP traffic. Just replace the variables in <> according to your environment.

Hope that helps.

-Mike

gdi · ‎09-10-2010

Mike - thank you for taking the time to reply - unfortunately I have tried what you have suggested, and smtp incoming still does not work.

My full config is below (default with only a port forward of the mail server - nothing else). Internet access from the inside works well through PAT.

Can you spot what is wrong with port forwarding of smtp?

Much much appreciated (beating my head against the wall with 8.3 trying to get a simple port forward to work).

Garth

: Saved
: Written by enable_15 at 20:17:39.058 UTC Fri Sep 10 2010
!
ASA Version 8.3(1)
!
hostname test
domain-name test.com
names
!
interface Vlan1
nameif inside
security-level 100
ip address 192.168.0.1 255.255.255.0
!
interface Vlan2
nameif outside
security-level 0
pppoe client vpdn group PPPoEGroup
ip address 1.1.1.1 255.255.255.255 pppoe setroute
!
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
!
ftp mode passive
object network obj_any
subnet 0.0.0.0 0.0.0.0
object network Mailserver
host 192.168.0.2
access-list outside_access_in extended permit tcp any any eq smtp
pager lines 24
logging enable
logging timestamp
logging asdm informational
logging facility 16
logging host inside 192.168.0.2
mtu outside 1500
mtu inside 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
asdm image disk0:/asdm-634.bin
no asdm history enable
arp timeout 14400
nat (inside,outside) source dynamic any interface
!
object network obj_any
nat (inside,outside) dynamic interface
object network Mailserver
nat (inside,outside) static interface service tcp smtp smtp
access-group outside_access_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
dynamic-access-policy-record DfltAccessPolicy
http server enable
http 192.168.0.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
crypto ipsec security-association lifetime seconds 28800
crypto ipsec security-association lifetime kilobytes 4608000
telnet 192.168.0.0 255.255.255.0 inside
telnet timeout 5
ssh timeout 5
console timeout 0
management-access inside
vpdn statements omitted
dhcpd auto_config outside
!

threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
webvpn
!
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
Cryptochecksum:omitted
: end

Nagaraja Thanthry · ‎09-10-2010

Hello,

Can you please try the following:

access-list outside_access_in line 1 permit tcp any host 192.168.0.2 eq 25

Hope this helps.

Regards,

NT

gdi · ‎09-10-2010

Thanks for the suggestion - I tried this and no change. I already had "any any" for port 25 access-rules...

Outgoing mail works, but nothing can come in...

Any other suggestions? Total brick wall here...

Nagaraja Thanthry · ‎09-10-2010

Hello,

What is the default gateway of the Mail server? Can you browse internet from

your mail server?

Regards,

NT

gdi · ‎09-10-2010

All internal computers (including the mail server) can browse the internet with the firewall inside port as their gateway - this indicates PAT is working fine from the inside going out.

It is only the outside mail that is unable to be port forwarded to the inside...

Help!

Nagaraja Thanthry · ‎09-10-2010

Hello,

Have you tried to telnet to the mail server from outside? Please try telnet

to outside interface IP of the firewall on port 25 (from internet) and see

if the connection opens. Also, once the attempt is done, check the

access-list (show access-list) to see if you are seeing any hit counts for

any rules. That should tell us if the traffic is hitting the firewall or

not.

Regards,

NT