Subnet connected devices to recieve WAN IP's from DHCP

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chrida

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Jul 29, 2015
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Hello everyone,

I have a problem, for which I can seem to find no solution or suiting thread.

I am in a dorm where I am allowed to use up to 7 static IP's (10.149.50.112-9) through one ethernet port only. My solution to servicing all of my devices w/o the hussle of assigning static IP's to each of them has been that of using an old router (TP-Link, TD-VG3631), assign to that one of the static IP's and use the router as gateway.

All fine, except I have a very, very annoying limitation on the number of packets I can send and receive on the net, and if I pass that limit the connection is blocked for 15 minutes.
The limitation is bundeled to an IP, thus then changing the static IP from the router config solves the problem (for about 10 minutes, you can imagine all the nice background network accesses by computer, tablet and smartphone already amount to so many packet exchanges, that the net gets blocked).

I would like to know if it is possible to set up the router to give away the 6 (as one is the router itself) IP addresses I was assigned in a DHCP fasion and then the devices connected to the router "skip" the router itself and connect to the WAN directly...


Thanks in advance,
Chris
 
Solution
jsmithepa
Well thank you first for stating your issue clearly, a breath of fresh air in this forum. :)

I THINK I got it. :D (maybe). Don't use your router between the college and your devices. Simply plug in an 8-port switch to the wall's jack, and plug in your router as one of the devices into the switch, the router will act as a DHCP ONLY and not doing any routing.

This assuming the college's doesn't go berserk and just ignores your DHCP requests.

Hope it works! :D
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jsmithepa

jsmithepa

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Jun 14, 2014
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Well thank you first for stating your issue clearly, a breath of fresh air in this forum. :)

I THINK I got it. :D (maybe). Don't use your router between the college and your devices. Simply plug in an 8-port switch to the wall's jack, and plug in your router as one of the devices into the switch, the router will act as a DHCP ONLY and not doing any routing.

This assuming the college's doesn't go berserk and just ignores your DHCP requests.

Hope it works! :D
 
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bill001g

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Aug 9, 2012
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That is a strange block of ip. What is the subnet mask on the network. 7 usable ips would mean they have to assign a /28 but 112 would not be a usable address.

I suspect they assume you will just use a switch and static ip. It would be easier if they really routed the blocks to you but most people would not know what to do with that.

If you load dd-wrt on a router you can use a non statndard config. You can assign all the ip to loopback on the router it will then respond to arp for all the addresses. It of course does no good to have all the ip on the router. What you do NAT these addresses to your actual devices. Your router would assign 192.168.1.x to the lan for example and then 1-1 nat for each device. Still is almost a static configuration though. You can have it used the block of nat ip via a pool but it gets tricky to get it effectively use them.
 
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chrida

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Jul 29, 2015
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Thanks jsmithepa for your answer! I don't know though how your solution would solve my problem :( Clearly I'm as bad as explaining the situation as I thought :p But in my defense, it is a really weird setup... I'll try again, somehow more schematic:

The facts:

  • ■ I have one ethernet wall port
    ■ I can connect to the network via static addres, precisely the parameters are

    • ■ IP: 10.149.50.112-119
      ■ Mask: 255.255.255.0
      ■ Gateway: 10.149.50.1
      ■ Dns : google
    ■ I have x devices (never more than 6 at the time) that need to be connected (mostly via WiFi) which often change (I often host people and going through the process of setting up their connection with a static ip... just... countless hours).
    ■ I have an insane limitation on numer of packages per IP that can be sent/received on the net

What I would like to achieve is:

  • ■ Use one router connected to the one port to,
    ■ assign the devices that connect to it IP addresses in the range specified above, and allowing them to,
    ■ bypass the router once the DHCP configuration is recieved and become independent in the "wan" network of my uni (the router thus acting like a bridge + dhcp server, I guess w/o NAT)

Hope this makes a bit more sense :S



Yeah... I don't get their idea for the setup either! You either buy a switch and a wireless router to connect all ethernet capable devices with their own IP and the wireless ones through an AP... It would have definetly be easier if they either limited me to 1 IP but no block on packets or routed the blocks to me, but I guess 90% of the ppl in the dorm wouldn't know how to handle the situation.

I like the NAT 1:1 with multiple IP's on the router idea, though it sounds like very experimental :p Might give it a shot after my exams next week, when fucking up the router will make no difference :D
 
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jsmithepa

jsmithepa

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Jun 14, 2014
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I wasn't being sarcastic, you really did explained it well on your original post and needs no further explanation, OK you threw in a new piece of info, WIFI, but my solution still stands. Why makes you think it won't work?

Your current problem is, you are doing a local NAT, so as far as the college is concerned you are using a single IP, and that's undesirable under the circumstances.

So don't do local NAT, if the 1-1 NAT solutions works, then go for it.

My solution predicates on your WIFI router not doing any NAT, in fact not using the WAN port at all. Use it as a dumb WIFI access point, it *should* still route traffic between the ethernet ports and your WIFI devices. So when your devices, either via ethernet or WIFI make a DHCP request, your box will respond and you configure it to lease those 5 IP, the WIFI router itself will take 1 IP. Now the DHCP requests will also get shoot out the wall jack, reason why I said hopefully the college doesn't care and ignore them.

That's pretty detailed, I probably can't go further if you are unwilling to tell me where the problem maybe or even to try it out.

WALL ===> SWITCH ===> ROUTER LAN PORT ===> WIFI.
 
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