I can not ping...

[cyberfreek]

I have configured an Exchange 2000 server to send and receive email trhough a Pix 501. I am able to telnet from the outside to port 25 so I know the firewall is permiting smtp traffic. The firewall is also configured to allow DNS traffic. What I'm not able to do is tell anythingemail.com to redirect dns traffic from ns1.anythingemail.com to the DNS server I have configured, ns1.trinitymortgageloans.com, which is on the same box of the exchange server. I beleive anythingemail.com attempts to ping the new name server in question to confirm if the server exists. If that is the case, how can I configure the pix 501 to respond to the ping. Please keep in mind that I can ping e0, x.x.x.137, successfully but when pinging the WAN address, x.x.x.138, that is translated to the internal exchange server, it times out. Is there something else I am missing? Any suggestions is greatly appreciated.

Here is my configuration:

PIX Version 6.1(3)
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password
passwd
hostname
domain-name
fixup protocol ftp 21
fixup protocol http 80
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sqlnet 1521
fixup protocol sip 5060
fixup protocol skinny 2000
no fixup protocol smtp 25
names
name 192.168.x.x ???
access-list 100 permit icmp any any echo-reply
access-list 100 permit icmp any any time-exceeded
access-list 100 permit icmp any any unreachable
access-list 100 permit gre any any
access-list 100 permit tcp any host x.x.x.138 eq smtp
access-list 100 permit tcp any host x.x.x.138 eq domain
access-list 100 permit tcp any host x.x.x.138 eq www
access-list 100 permit udp any host x.x.x.138 eq domain
access-list 101 permit ip 192.168.x.x 255.255.255.0 192.x.x.x 255.255.255.0
access-list nonat permit ip 192.x.x.x 255.255.255.0 10.0.0.0 255.255.255.0
access-list nonat permit ip 192.x.x.x 255.255.255.0 192.x.x.x 255.255.255.0
access-list acl_out0 permit gre any any
pager lines 24
logging on
logging buffered errors
logging trap notifications
logging history notifications
interface ethernet0 10baset
interface ethernet1 10full
mtu outside 1500
mtu inside 1500
ip address outside x.x.x.137 255.255.255.248
ip address inside 192.x.x.x 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
ip local pool pptp-pool 10.0.0.1-10.0.0.5
pdm location 192.x.x.x 255.255.255.255 inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 x.x.x.140-x.x.x.141
global (outside) 1 interface
global (outside) 1 x.x.x.139
nat (inside) 0 access-list nonat
nat (inside) 1 192.x.x.x 255.255.255.0 0 0
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) 192.x.x.x x.x.x.138 netmask 255.255.255.255 0 0
static (inside,outside) x.x.x.x 192.x.x.x netmask 255.255.255.255 0 0
access-group 100 in interface outside
route outside 0.0.0.0 0.0.0.0 x.x.x.142 1
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h323 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
http server enable
http 192.x.x.x 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
no floodguard enable
sysopt connection permit-ipsec
sysopt connection permit-pptp
no sysopt route dnat
crypto ipsec transform-set tm1 esp-3des esp-md5-hmac
crypto map x 1 ipsec-isakmp
crypto map x 1 match address 101
crypto map x 1 set peer x.x.x.17
crypto map x 1 set transform-set tm1
crypto map x interface outside
isakmp enable outside
isakmp key **** address x.x.x.17 netmask 255.255.255.248
isakmp identity address
isakmp policy 1 authentication pre-share
isakmp policy 1 encryption 3des
isakmp policy 1 hash md5
isakmp policy 1 group 1
isakmp policy 1 lifetime 1000
telnet
telnet timeout 5
ssh timeout 5
vpdn group 1 accept dialin pptp
vpdn group 1 ppp authentication pap
vpdn group 1 ppp authentication chap
vpdn group 1 ppp authentication mschap
vpdn group 1 ppp encryption mppe auto
vpdn group 1 client configuration address local pptp-pool
vpdn group 1 pptp echo 60
vpdn group 1 client authentication local
vpdn username x password x
vpdn enable outside
dhcpd address 192.x.x.20-192.x.x.30 inside
dhcpd dns x.x.x.40 x.x.x.12
dhcpd wins 192.x.x.x
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
dhcpd enable inside
terminal width 80

 

[themut]

You will not be able to ping or access the public IP address of your internal server unless you use the alias command, but you need an outside DNS server for the alias command to work so the PIX can see the DNS request and "fix" the DNS response. Take a look at the link below explaining how to configure the alias command:

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a0080094aee.shtml

You need to configure the DNS doctoring feature. If you still experience problems then I'd suggest you set up a syslog server to find out the reason why it is denied. The link below will help you set up a syslog server:

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a0080094030.shtml

For troubleshooting use level 7 and once you find out the root of the problem you can leave the PIX logging at level 4. You can search the web for any syslog server, use the keywords "syslog daemon". Kiwi is a pretty good syslog server.

 

[cyberfreek]

themut

Thank you for the quick response. Is there another way I can have the DNS inside? Unfortunately, my client does not have the resources to setup an external DNS.

 

[themut]

Unfortunately no because the DNS request must pass through the PIX so the reply can be fixed by the PIX. If the DNS request is not seen by the PIX then there´s no way to fix the reply. Can you configure the server to look for the private IP address instead of the public one?

 

[cyberfreek]

themut

I'm sorry. What do you mean can I configure the server to look for the private ip address instead of the public one?

 

[cyberfreek]

Thanks for the advice. I went ahead and hosted the DNS.
They have been working for some time now.