[TriLUG] Off Topic: Need Cisco Router Config Help

Tarus Balog tarus at opennms.org
Thu Apr 3 20:53:10 EDT 2008

On Apr 3, 2008, at 7:32 PM, Chris Bullock wrote:
> First thing I would do is without the help of the host file try to  
> ping
> private.opennms.com and see what you get.  Then perform a dig or  
> nslookup
> to see exactly what DNS server gave you that IP.

It's definitely not a DNS issue. It's a NAT issue.

Let's assume the external address is and the internal LAN is

If www.example.com points to, the router will NAT port 80 to

 From outside the LAN, http://www.example.com works fine.

 From inside the LAN, http://www.example.com connects to the router's  
HTTP server (, thus NAT is not working from the LAN.

The *workaround* is to set, on the LAN, www.example.com to point to

Now, when the router was a Linksys, www.example.com worked in all  
places. I was wondering if there was something in the way Cisco does  
NAT to make that work as well.


Tarus Balog, OpenNMS Maintainer             Main:   +1 919 533 0160
The OpenNMS Group, Inc.                     Fax:    +1 503 961 7746
Email: tarus at opennms.org                    URL: http://www.opennms.org
PGP Key Fingerprint: 8945 8521 9771 FEC9 5481  512B FECA 11D2 FD82 B45C

More information about the TriLUG mailing list