Expanding the home network
February 20, 2006 3:19 PM   Subscribe

This is probably an embarassingly easy question to answer, but when it comes to networking, I'm clueless. Can I use static IP + DHCP on same network using two routers—one wired/one wireless?

I have a DSL connection with five (way too expensive) sticky/static IP addresses. I use the SBC-supplied DSL modem as a straight-through router. Three Linux boxes (two servers, one desktop) connect via the DSL modem/router, each claiming a static IP. That leaves one port on the DSL router and two IP addys.

I have recently picked up an iBook and, while I can hook up to that remaining port on the DSL modem/router, I'd like to do the wireless thing instead. I'd also like to do this using DHCP instead of assigning the laptop a static IP. I'm also getting to a point where just handing out IP addys to my collection of toys isn't going to work. it's a very nice problem to have and I'm definitely not complaining

Basically, can I conenct a wireless router into the remaining port on the DSL modem and configure it such that it runs a DHCP service while the other three connections still use the straight-through, static IP setup? Will the wireless router require one of the static IPs or can it just refer to the gateway IP?

BTW: I've looked into using one of the Linux boxes as a wireless DHCP service via a wireless PCI card but that looked exceedingly tedious, even for Gentoo. I'm sort of hoping this is the quick and easy answer to my problem.
posted by Fezboy! to Computers & Internet (10 answers total)
Yes. Assuming the static addressess are external IP addresses and the DHCP entries will be 192.168.whatever, you can setup your Wireless Access Point (WAP) to be the DCHP and Network Address Translation (NAT) server for your wireless (and wired if you want) network. The WAP would be the gateway for all the DHCPed devices.

This may cause some routing problems between the static IP addresses and the DHCP addresses, but there should be somewhere to set that too.
posted by krisjohn at 3:29 PM on February 20, 2006

The straight forward way of doing what you want is to let the wireless router have one of your 5 public IP addresses as its WAN port, turn on NAT (usually the default for most Linksys and DLink type SOHO wireless routers), and turn on DHCP on the wireless router. As far as the wireless router is concerned, it will need the gateway address for your public IP subnet as its gateway address, and you should give it your ISP's DNS servers IP addresses.

You can usually specify separate sub-nets for the wireless and wired ports on these SOHO wireless routers. Say, give its 4 wired ports 192.168.100.x net addresses, and start your wireless DHCP range at 192.168.101.x It's good practice to limit your DHCP ranges to sane values (5 or 10 addresses) to limit the number of connections to something reasonable.
posted by paulsc at 3:30 PM on February 20, 2006

The wireless router probably requires one of the static IPs (which it will share between all connected clients), but otherwise this will be no problem.
posted by cillit bang at 3:30 PM on February 20, 2006

Yes, you can connect a wireless router on the remaining port on the DSL/Router. The Wireless router will require an IP from your available pool. The wireless router will more than likely require you to use a private IP range (in either the 192.168.XXX.XXX range or 10.10.XXX.XXX range.) This means that you will be down to one open static IP.

Numerous wireless routers also have 10/100Mbit ethernet support as well, which means you can have a few (read 255) machines on your non-publicly addressable network segment.
posted by PROD_TPSL at 3:36 PM on February 20, 2006

Sweet! I'm off to the store...
posted by Fezboy! at 3:42 PM on February 20, 2006

I should add that while I only marked two as best answer, all addressed facets of my questions and combine to form some kind of mega best answer. Y'all can connect to my WAP anytime you want!
posted by Fezboy! at 3:46 PM on February 20, 2006

Just FYI, the private (RFC1918) ranges are:

10/8 (10.x.x.x)
172/12 (172.16.x.x - 172.31.y.y)
192.168/16 (192.168.x.x)

Not directly important but hey, may as well be complete. :)
posted by kcm at 4:17 PM on February 20, 2006

er, 172.16/12.
posted by kcm at 4:18 PM on February 20, 2006

I'm not sure how clearly this was stated.

If the DSL modem is not acting as a router, rather it is acting as a bridge modem, you can install a wireless router as a gateway for the Ibook.
As long as the modem isn't using NAT, you should be good.
the router should be configured for PPPOE and connecting to pull one of your 5 IP's.
I would also strongly recommend changing the default password for the new router and blocking any MAC but the ibook from the wireless lan.
posted by Megafly at 5:46 PM on February 20, 2006

"Thanks again, all," he posts from his butterfly chair located rooms away from the server bench.

Not sure if I have the terminology right, Megafly, but I think you're right when you mention that I am running the modem as a bridge. At any rate I plugged the wireless router into the modem, assigned it one of the free static IPs, changed the admin and user passwords, tossed together a 26 character WEP string and enabled 128bit WEP, verified NAT was enabled, and then named the access point Motherfucker.

that last part is a joke. what else could I call it other than FezNet?

Thanks again everyone. You're all beautiful snowflakes.
posted by Fezboy! at 7:15 PM on February 20, 2006

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