PIX doesn't NAT outbound packets to correct IP

Answered Question
Oct 4th, 2007

Hello all,

I have a PIX 515E running v6.1(2). The firewall has an external and internal interface only. The webservers and mail server are behind the firewall on the internal network. We have 1 external address reserved for all outbound connections from PCs. I have several static configurations set for inbound connections to the web and mail servers.

The mail server is using an external address of XXX.XXX.XXX.105 which the PIX passes through to my internal address of XXX.XXX.XXX.24. The outbound connections from XXX.XXX.XXX.24 end up using the external address of XXX.XXX.XXX.109. I need it to use the 105 address so other mailservers will accept our emails. I understand from my reading is that all I need is the static config and an access-list entry for outbound-in connections to make it all possible.

What am I doing wrong? Any information would be appreciated. Following is the relevant config:

nameif ethernet0 outside security0

nameif ethernet1 inside security100


name XXX.XXX.XX6.109 extnat

name XXX.XXX.XX6.105 extmail

name XXX.XXX.XX8.24 intmail


access-list 111 permit tcp any host extmail eq smtp

access-list 211 permit ip XXX.XXX.XX8.0 XXX.XXX.X10.0


global (outside) 1 extnat

nat (inside) 0 access-list 211

nat (inside) 1 0 0


static (inside, outside) extmail intmail netmask 0 0


access-group 111 in interface outside

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0 votes
Correct Answer by sundar.palaniappan about 9 years 3 weeks ago

The configuration looks good. After you added the static did you do a 'clear xlate' for the static to take effect?

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Overall Rating: 5 (1 ratings)
Correct Answer
sundar.palaniappan Thu, 10/04/2007 - 12:36

The configuration looks good. After you added the static did you do a 'clear xlate' for the static to take effect?

tshooter91 Fri, 10/05/2007 - 08:53

I did as you suggested and I'm not getting bounced emails any more, so that must've fixed it.

Come to think of it, the mail server _was_ moved to different hardware, so maybe something with the MAC address was still hung up in the translation tables?

Thanks for the fix. A reload of the PIX didn't work, but running that command did.


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