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Author Topic: Static IP and dynamic IP on the same router  (Read 2841 times)

fozzie bear

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Static IP and dynamic IP on the same router
« on: April 27, 2009, 04:08:29 PM »

I am trying to configure my network to the best effect but although I have a reasonable knowledge of networks port forwarding and TCP/IP etc I would like some advice on a proposed setup.
The configuration of my two ADSL circuits to date is as follows:-

First ADSL - Enta adsl circuit with dynamic WAN ip attached to a 3 com router with NAT enabled and DHCP enabled for the LAN which has a private address range.  This is my main network with up to 10Pcs laptops and servers attached to the LAN and used for e-mail web access etc.

Second ADSL - Enta adsl circuit for backup purposes and external access with a block of 8 static IP addresses This circuit is connected to a D-Link DSL-G604T router with NAT currently disabled.
One IP address is assigned to the router WAN port (, the second to the router itself (, leaving to 143 as usable IP addresses as the first and last of the block 136 and 144 are not useable.
This adsl is for hosting a web server, ftp server and now a Windows Home Server which will probably replace both the former. I also want to use it for backup should the first adsl go down. My file server and Windows Home server are both dual homed with one nic assigned one of the usable static IP addresses and the second NIC configured for DHCP so that it picks up a private IP address from the 3Com router. The lan is gigabit enabled with gigabit NICS and 16 port gigabit switch so that I can stream dvds and large files around the local network. What I would like to know is if it is possible to have both static routes and dynamic routes configured on the same router (D-Link DSL-G604T) ?. For example can I assign a static IP address to the internet facing nic of the WHS but have the remaining IP addresses 140-143 delivered by DHCP.  The reason for doing this is to change ADSL gateways should one go down we would only have to disconnect from one wireless SSID (on the 3Com) and connect to the SSID on the other(D-Link network), without having to reconfigure the PC/Laptop with a static IP.

I assume that I would have to reconfigure NAT on the D-Link router so that I can enable DHCP on the D-Link LAN?

The question is how do I deal with the static IP allocation? Do I just open all the ports? Do I  port forward the relevant ports ie ftp, https, RDP etc to the client(s) with the fixed IPs.

Alternatively should I just put the Static IP client(s) in the DMZ of the router (assuming this can be done on the G406T)?

This may seem a lot of work to share out a handful of IP addresses but I need something that is easy for my wife to change gateways but also allows the use of the static addresses to allow remote access and my web server to be available.

Any help or advice on this would be appreciated.
regards Fozzie