08-18-2006 10:19 AM - edited 02-21-2020 01:07 AM
I have installed a PIX firewall instead of our old belkin router, but just cant get my internal exchange server to work right.
the mails are left in a queue with the information: "smtp could not find any DNS server"
That a pretty strange information considering that i have no problem browsing the internet from the server and clients. ive tried to open up for http, smtp and www to get the mailing to work but it seems that i get a DNS problem on the server in return. 192.168.1.200 is the mail server.
PIX Version 6.3(5)
interface ethernet0 auto
interface ethernet1 100full
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password xxx
passwd xxx
hostname pixfirewall
domain-name agms
fixup protocol dns maximum-length 4096
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
access-list outside_access_in permit tcp any eq smtp host 83.91.26.149 eq smtp
access-list outside_access_in permit tcp any eq https host 83.91.26.149 eq https
access-list outside_access_in permit tcp any eq www host 83.91.26.149 eq www
access-group outside_access_in in interface outside
pager lines 24
mtu outside 1500
mtu inside 1500
ip address outside dhcp setroute
ip address inside 192.168.1.1 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) 192.168.1.200 83.91.26.149 netmask 255.255.255.255 0 0
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout sip-disconnect 0:02:00 sip-invite 0:03:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server TACACS+ max-failed-attempts 3
aaa-server TACACS+ deadtime 10
aaa-server RADIUS protocol radius
aaa-server RADIUS max-failed-attempts 3
aaa-server RADIUS deadtime 10
aaa-server LOCAL protocol local
http server enable
http 192.168.1.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
telnet timeout 5
ssh timeout 5
console timeout 0
dhcpd address 192.168.1.2-192.168.1.33 inside
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
terminal width 80
Cryptochecksum:xxx
: end
please let me know what you see. ive been trying to get it to work for 3 days. first i was sure that i had made a mistake when trying to open port 25 but my server complain about DNS in the mail queue. thanks in advance
08-18-2006 12:13 PM
Make the following changes and see what happens...
access-list outside_access_in permit tcp any host 83.91.26.149 eq smtp
access-list outside_access_in permit tcp any host 83.91.26.149 eq https
access-list outside_access_in permit tcp any host 83.91.26.149 eq www
static (inside,outside) 83.91.26.149 192.168.1.200
If this helps,please rate.
Cheers.
08-18-2006 12:15 PM
Are you sure that your smtp server service is running?
08-18-2006 01:10 PM
yes the service is running because everytime i change the pix with the belkin wireless/router, all problems are gone. but i need VPN support.
jwalker, ill try it first thing tomorrow.
08-18-2006 02:56 PM
Hello,
1. Does the exchange have internet connection?
2. Can you try to use the browser or nslookup to see if it can reach the DNS servers.
3. Another thing is try to remove the smpt inspection
no fixup protocol smtp 25
Let me know if the above solves the problem
Regards,
08-18-2006 02:58 PM
By the way your access list from outside to inside is incorrect. It should be like this
access-list outside_access_in permit tcp any host 83.91.26.149 eq smtp
access-list outside_access_in permit tcp any host 83.91.26.149 eq https
access-list outside_access_in permit tcp any host 83.91.26.149 eq www
Let me know if this solves the problem,.
Regards,
08-18-2006 10:53 PM
okay i will try the access lists.
yes the server has internet access. i tested this by browsing the internet, so DNS is working.
ive talked to the administrator who installed the server and i think the DNS error message might not be accurate. its just an indication that the mail server cannot send or recive. i need to run a few more test today so i can make sure which way is the problem, in or out.
08-19-2006 02:13 AM
The access-lists you wrote must be wrong too because if i default the pix im able to brows the internet fine, from ALL clients (192.168.1.x). when i type in this:
access-list outside_access_in permit tcp any host 83.91.26.149 eq www
static (inside,outside) 83.91.26.149 192.168.1.200
OR this:
access-list outside_access_in permit tcp any host 83.91.26.149 eq www
static (inside,outside) 83.91.26.149 192.168.1.200
access-group outside_access_in in interface outside
i can no longer brows anything. as soon as i reverse those two commands, i can brows again.
08-19-2006 05:19 AM
To get this to work, you will need to first make the static which translates hosts on a security zone to another security zone..
So
static (inside,outside) 83.91.26.149 192.168.1.200
Then you need to make an access-list, to allow the hosts on the lower sec zone (outside) access to your statically translated host on the inside..
access-list outside_access_in permit tcp any host 83.91.26.149 eq www
Then you need to apply the access-list to the outside interface...
access-group outside_access_in in interface outside
NOTE: This is for inbound traffic ONLY!! If you do not have another ACL on the inside interface (and access group), then ALL traffic will be allowed because it is the highest security zone (without ACLs security zones apply). Also, hosts coming from the outside are only allowed to access 192.168.1.200 using the current ACL. If you need smtp access, then use
access-list outside_access_in permit tcp any host 83.91.26.149 eq smtp
as well...
08-19-2006 05:25 AM
yes, so far so good. with these commands im able to recive email (not send) and still brows the network
no fixup protocol smtp n25
access-list outside_in permit tcp any interface outside eq smtp
static (inside,outside) tcp interface smtp 192.168.1.200 smtp netmask 255.255.255.255 0 0
access-group outside_in in interface outside
again, im not able to send mails. its very weird since i have no restrictions outbound. ill paste the whole configuration:
PIX Version 6.3(5)
interface ethernet0 auto
interface ethernet1 100full
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password upF9MmPO.s3wsSNX encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname pixfirewall
domain-name agms.dk
fixup protocol dns maximum-length 4096
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
no fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
access-list outside_in permit tcp any interface outside eq smtp
pager lines 24
mtu outside 1500
mtu inside 1500
ip address outside dhcp setroute
ip address inside 192.168.1.1 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm location 192.168.1.200 255.255.255.255 inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) tcp interface smtp 192.168.1.200 smtp netmask 255.255.255.255 0 0
access-group outside_in in interface outside
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout sip-disconnect 0:02:00 sip-invite 0:03:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server TACACS+ max-failed-attempts 3
aaa-server TACACS+ deadtime 10
aaa-server RADIUS protocol radius
aaa-server RADIUS max-failed-attempts 3
aaa-server RADIUS deadtime 10
aaa-server LOCAL protocol local
http server enable
http 192.168.1.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
telnet timeout 5
ssh timeout 5
console timeout 0
dhcpd address 192.168.1.2-192.168.1.33 inside
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
terminal width 80
Cryptochecksum:xxxx
: end
pixfirewall#
do you see any problems?
08-19-2006 09:22 AM
okay, maybe i should just assume the PIX is bugged and get RMA. i mean, ive never in my 10 years of networking seen so many problems trying to get an exchange server to SEND mail through a firewall from the inside to the outside.
Even with minimal configuration this should be possible, right? by minimum i mean just enough configuration to support all the internal network with internet access and then maybe with the "no fixup protocol smtp 25" added?
The reason why i mention "fixup" is because thats all i ever find trying to google for a solution. it just didnt help me.
08-19-2006 05:22 AM
Hello,
just a friendly reminder to everyone to please sanitize your configurations before you post them on a public web site such as this. Here we have a config for a PIX that appears to be complete. Having that config is a master key to your security door for anyone that knows what they are doing.
Sorry to be the heavy but it needs to be said
08-19-2006 11:06 AM
You may try adding an acl on the inside (that allows all IP) interface to see if that solves the issue..
access-list inside_access permit ip any any
access-group inside_access in interface inside
08-19-2006 11:42 AM
thx but i already tried that in my desperation earlier today.
08-20-2006 05:56 AM
i finally found the error!
the problem was a misconfigured SMTP DNS IP. on the exchange server, there is a protocol folder where also SMTP has its info. when sending a mail, SMTP is sending 2 quieries using UDP to resolve the domain (hotmail.com, yahoo.com etc.) This IP was set to the internal IP of the gateway (inside address). Somehow the old belkin router resolved this request from the server by default but the pix does not. This IP should not have been set to the inside address, but instead to the ISP external DNS address. as soon as i did that, all mails were send out the PIX.
Thanks all for your help. it was great!
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