Port Forwarding with Cisco 871??

I hope somebody has some ideas on this, cause it's making me crazy. It's probably something dirt simple I'm overlooking.

We have a Netopia DSL "modem", which provides us with four static IP's.

We take one of those IPs, and run it to a CISCO 871 (which provides a VPN that I don't think is pertinent to the problem.). The CISCO is also doing DHCP, and NATing to a 192.168.0.x LAN.

All seems to be working fine, until I try to "Port forward" Ports 25,

80, and 110 from the outside WAN through to a server on the LAN.

The Netopia seems to be doing it's part -- I've configured what Netopia calls "pinholes", and if I hang a server directly off of it, I can access the required ports from the outside.

The CISCO has been configured by a CISCO tech, via Telnet from their support center. He basically put in "permit any to eq 80" (I'm not sure of the exact syntax) on the inbound, and "permit to any eq 80" on the outbound. ((He also put in "permit" statements for the other ports).

Problem is, it's not working. I get no response from anything on the LAN when I try to access it from outside. I've checked the CISCO's logs, and can't even find a record of the attempts at access, although I may not have all the logging I should enabled (I'm not super-familiar with CISCO stuff).

I get the same results no matter which port I try.

Any thoughts? Suggestions for troubleshooting methods? Is there some basic routing/networking reason why this won't work? Seems I've done this dozens of times before with Linksys, Dlink and the like without problems.


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The problem you describe can be solved with NAT. You need to add a static translation for ports 25, 80 and 110 of one of the public IP's to the designated internal private IP.

ip nat inside source static tcp 25 a.b.c.d 25 ip nat inside source static tcp 80 a.b.c.d 80 ip nat inside source static tcp 110 a.b.c.d 110

(replace a.b.c.d with the public IP of the outside interface (or any of the other public ip's).


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Erik Tamminga

Thanks Eric! I'll be able to give it a try tomorrow.

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