SMTP IP address issue

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Feb 16th, 2009
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I have a Cisco 1811 Intergrated Services Router which has been in operation for over a year. It also provides VPN access for the Cisco dialer VPN and three small remote offices with PIX 501s connected back to the main office. All worked well, except I discovered the outbound e-mail came from an incorrect IP address. I want the SMTP to show from, but it shows from is the e-mail server. I used the command "ip nat inside source static tcp 25 25 extendable". E-mail comes in OK, but outbound e-mail shows the primary IP address of the router, not the address in the IP NAT line. The server is also a DNS/WINS server. I do not want to change the public DNS records. I have tried some changes, but each try created a different problem.

Attached is a copy of the full config.


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Giuseppe Larosa Mon, 02/16/2009 - 10:08
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Hello Ross,

I would rewrite the ACL 100 to deny host

before the line

permit ip any


deny ip host any

in this way the NAT is managed by the static entries

Hope to help


rossmartin Mon, 02/16/2009 - 16:16
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Due to their schedule, I will not be able to try it until tomorrow PM. I will try it then. Thanks for the suggestion.


rossmartin Tue, 02/17/2009 - 16:33
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I added the deny line. Inbound works fine. My server cannot access the internet. It cannot reach dns forwarders, ping, or browse the internt. Other inside hosts have internet access (except names are not being resolved) Here is my access lit 100. Is it in the right order?

access-list 100 deny ip

access-list 100 deny ip

access-list 100 deny ip

access-list 100 deny ip

access-list 100 deny ip host any

access-list 100 permit ip any


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