Networking newbie question: We have business cable service and it includes 3 fixed IP addresses. I have forwarded a couple ports (Jabber, MySQL) on our router (CISCO RV802) to our internal server. Just a classic port forwarding setup.

When I try to connect from an external client to the services on the forwarded ports using one of our external IPs the connection fails. However if I use the external IP of the router I am able to connect. So let's say my fixed range is and my router's IP (as reported by tracert.com) is It appears that I need to somehow set things up so the fixed IPs route to the router.

Looking at the web management interface for my router I came across One-to-One NAT which sounded promising but when I set a rule to map the public IP range (73,74,75) to my private address of the router I received an error:

LAN Port IP Address was in the Private IP Range. You can't add any more.

Like I said, I'm a newb and just barely grasp how all this is interconnected so it could be the solution is simple and I'm just missing it. I'd appreciate any guidance at this point.

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    If you have 3 fixed IPs (from Cox) then why does the provider (Cox) assigns a dynamic one to your router? They have to map the IPs to the router. – mailq Sep 8 '11 at 20:04
  • I have the router setup to "Obtain IP Address Automatically" because when I key in the IP address data from COX the connection is INCREDIBLY unstable (a ping will work 4 times, then fail for the next 20, then work once, then fail some more, etc.) – Steve K Sep 8 '11 at 20:22
  • You need to discuss this with Cox. – mailq Sep 8 '11 at 20:27
  • Yeah, I think I may put another call in. God knows we give them enough money every month that they can TRY to help me instead of "You'll need to call the router manufacturer" ARGH! – Steve K Sep 8 '11 at 20:30

You have to manually enter the ip information into the router... the router should not be accepting IP's via DHCP from the ISP... Add one of the fixed ips in the Static IP address entries with the dns servers supplied and you should have no problem.. Have your ISP assign a DNS name to the IP Address so you can get to it by name... mycompanyserver.domain.com

FYI: What kind of router is it?

  • It's a Linksys (now Cisco) RV082. It wasn't cheap and it was supposed to be a failover router for our backup DSL and it has never once properly handled that task :( – Steve K Sep 8 '11 at 20:24
  • How should that work if the ISP does not route the IPs to the router?! – mailq Sep 8 '11 at 20:25
  • I'm assuming you are referring to the "WAN" info? As I mentioned in the comment to mailq - when I enter the IP information into the router it becomes terribly unstable. If I select the "Obtain an IP Automatically" it seems to work just great. – Steve K Sep 8 '11 at 20:27
  • When I inspect the IPs the router pulls from COX I can see that they are ALL different from what they have provided me on paper. I've confirmed with them twice that what they supplied me is correct. My knowledge is so limited though that I don't have the confidence to argue with them because it could be I've done something wrong. – Steve K Sep 8 '11 at 20:28
  • That is the way we did it on Cablevisions network... I know different ISPs... Thought it could work. Sounds like something is not right, Does COX require M.A.C. Registration? – David Sep 8 '11 at 20:30

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