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1 to 1 Nat Issues


1 to 1 Nat Issues

We just became a Comcast customer and have the Cisco DPC3939B with 5 Static IPs.


For some reason, 1 to 1 NAT does not work, it performs very slow  from the outside to a point of failure, and the PC on the LAN side that is in the NAT table is extremley slow accessing the Internet?

Can this modem support this feature? Or do we need to go an purchase a firewall/router for this to work? Could my firmware need updating?


Is anybody using the 1 to 1 Nat feature? 


We are trying to utilize the 5 IP addresses to 2 different servers behind the Comcast Gateway. We setup  NAT per public IP address to internal IP server and use the port mgmt to allow specific ports. However, this does not work. It runs extremely slow and eventually it fails. I can see other people having similar problems:


It appears that you need your own equipment, which is too bad, as Comcast should provide a workable solution to basic NAT.

Respected Member

Re: 1 to 1 Nat Issues

Hello IT_Tech and welcome to forums,


I apologize for the delayed response to your post. At this time I can confirm that the 1-to-1 NAT feature does work on our gateways but we in the community would require more information to your network configuration in order to better help. Without giving specific IP information would you explain in more detail your need for using the 1-to-1 NAT feature so we can help?


Thank You

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