Problem with Cisco 1700 Router setup

[eclipse2000]

I have just purchased and setup a Cisco 1700 ADSL router which is  working lovely, i have 5 static IP addresses assigned by BT so these  have all been configured through NAT and the firewall and remotely we  can access our servers etc fine.

The problem im having is with our  iphones, on the email settings we have our mail server set to  mail.xxxxxxxxx.co.uk which this resolves to 217.xxx.xxx.xxx which is one  of our static IP's. So when remotely i can access mail fine over a 3G  connection, but when at the office on wifi which is through this router  doing all the work im not able to connect to emails.

I think its something to do with the mail server hostname and the static IP browsing this on a local connection.

Im sure i need to allow something in either NAT or the Firewall but i have hit a blank. Any help with this issue would be great.

Many thanks

Paul

[andtoth · Accepted solution]

Hi Paul,

Likely you are using static NAT entries to map outside addresses to the inside email server address and TCP ports.

I reckon this is not working because the client on wireless tries to reach the server on the external IP so it reaches the router which does not know where to translate that packet because NAT portforward is triggered when coming from outside.

Try creating the static NAT entry on the router by mapping a single external address to a single internal address, rather than mapping specific ports only or using overload.

If that does not help, consider using Split DNS (called DNS doctoring in firewall terminology). With that, you can have your internal DNS server to respond with the internal IP address of the email server when a client queries for the email server address. Then your internal clients will easily reach the email server, without the need to reach the router.

Best regards,

Andras

[eclipse2000]

Thanks for your reply Andras.

24 hours before this reply and we managed to resolve this by doing what

you have just said and its sorted the issue out fine.

Many thanks

[andtoth]

Hi Paul,

Thanks for the feedback, glad to hear you have resolved this.

Please don't forget to mark this post as answered.

Best regards,

Andras