Route Traffic out and back in with multiple public IP

[kevenpenner]

Hi guys,

I have a Cisco 1841.

I have two public IP's bound to the outside interface with ip nat outside.

I have the inside interface setup with two internal IP's with ip nat inside

I need internal host (mailserver) A to send mail to internal host (mailserver) B.

DNS resovles the mailservers to their public IP's. But when they try to connect they are blocked. I believe I need a nat entry to accomplish this but I cannot find one on the support forums... Any help is appreciated!

Host A 192.168.0.1

Sends mail out through 1.1.1.1

Needs to come back in through 2.2.2.2 (Secondary public IP)

And arrive at Host B 192.168.100.1

Inside interface has 192.168.0.254 as main IP and 192.168.100.254 as secondary IP.

Outside interface has 1.1.1.1 as main IP and 2.2.2.2 as secondary IP.

ACL's are disabled when I test. Both hosts have full internet access. Default route assigned on the router is in the 1.1.1.1 subnet.

[John Blakley]

Do these really need to speak to the outside address? If they only talk to each other internally, you should configure your internal dns, if you have one, to resolve to the internal address of the mail server instead of the outside. Otherwise, I would edit the hosts file on each machine to point the hostname that you're going to to the internal address and be done.

If this is a windows machine, the hosts file is at c:\windows\system32\drivers\etc\hosts. If your maillB server is 192.168.1.50, you would edit the mailA server hosts file and add the line:

192.168.1.50      mailb.mymail.com

mailb.mymail.com is the smtp server that your mailA is doing your current lookup on. The hosts file is used before any dns server, so if there isn't an entry in the hosts file, it will roll over to dns and not affect anything else.

HTH,
John

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[kevenpenner]

I have a lot of domains on the two different servers, and I would have to manually enter either the host entry or the domain on an internal DNS manually everytime another domain is added to the mail server, its a lot of extra work to keep track of. Allowing it to go out and back through the router would be ideal.