Conflicting systems (network setup problem)

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Conflicting systems (network setup problem)

Postby filecore » Mon Mar 23, 2009 12:46 pm

Okay, this is complex. I've taken over network and computer support in a voluntary organisation and it's all a bit of a mess. They have a four-port ADSL modem/router, which seems to hand out unique IPs to all computers connected to it. It theoretically uses a 10.0.0.x internal network, but none of the computers (on DHCP) see this - only external IPs in the 80.x range. To access its admin interface, I have to manually set a static IP of 10.0.0.x and lose internet access for the duration.

To complicate matters, they have a cheapie four-port wireless router (local brand) to supply wireless. One wire leads from the modem into the wireless router's port 1. The wireless router is on an internal network of 192.168.x, but again, any computers connected get an 80.x public IP rather than an internal IP. I've tried my best but can't see how this is happening.

Finally, they have a network-enabled printer (HP 2600n) which is currently set with an internal IP in the 192.168.x range, although naturally they can't use it as a network printer because of the mangled state of their network, and it's connected by USB only. This isn't really a problem - it's a doddle, once I get the internal network operating properly - it's more just to indicate what a mess the whole thing is.

Now, I know I haven't given much detail, but that's because these are horrid devices with badly-writen user interfaces, and they're models (and brands) that aren't really available anywhere else, customised for certain local distributors. Basically my question boils down to this: first, is there any way I can make this work with a 10.x and 192.x devices in the same internal network?

And secondly, although I've tried connecting everything to the wireless router and only having the net connection going via the modem, it doesn't work - I can have all IPs on the internal network without internet access, or all having unique IPs on the internet but no internal network. I can't find a way to disable the routing functions of the modem (it's an A-Link Roadrunner 40C/44C). Am I better off just scrapping all of this and getting a new, single device?
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Postby evasive » Mon Mar 23, 2009 1:35 pm

Not sure how the first device directly connected to the internet is configured but that sounds like the culprit. You want that to actually route instead of bridge like it appears to do now.

Once you have that sorted (e.g. only private addresses on one side and 1 public address on the outside) you can start thinking about putting in one or more switches on the inside and kick out any superfluous routing stuff.

you can have 10.x and 192.168.a.x on your network on the inside as long as you have a router between the networks with no filtering at all.
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Postby filecore » Mon Mar 23, 2009 1:46 pm

As I said, first device is router/modem, so ADSL comes in via phone line straight into it, and its router functions provide internet out. It looks more or less like this and has the following ports on the reverse: power, RJ-11 in, 4x RJ45 out. Its interface is really terrible (I can export it as HTML if you want to see for yourself) but there is no option to set it into bridge mode only. I've been prodding at this for a while now and I can't see any way round it - even removing the wireless router, and having the A-Link as the only device, I still can't get a 10.x internal network running happily (all machines have different 80.x public IPs with a common 80.119.x default gateway. I'm coming to the conclusion that the modem/router is a piece of crap.
Home server: Asus P5Q Pro, Core2Quad, 8GB DDR2, ENGTX260 876MB, Zalman 800w, Antec P180 case, 2x1TB and 2x2TB Samsung Spinpoint F1, Windows 7 64-bit, etc

Work server: HP ProLiant ML350 G6, hexacore Xeon E5645 2.4GHz (12 logical cores), 16GB DDR3, 3x300GB SAS RAID5, Server 2008 R2, nVidia GT560Ti 1GB for Hyper-V RemoteFX acceleration
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Postby evasive » Tue Mar 24, 2009 12:58 am

If that is the device in question (A-link RR24) then there's no surprise as it can be had for $27,44 which is very little money for a modem/router.

So, yes, ditch this POS stuff, get a modem/router with wireless and a switch if you need more than the 4 ports that usually come with such a beast.

Before you do so though you need to find out what device or machine is dishing out public IP addresses on your devices. This means going to the modem/router, disconnecting everything, putting in a PC and see what address it gets from the DHCP in that modem/router. If that is a public address then you can solve that little problem too. If not you can now cut the rest of your network into sections and see where the rogue DHCP-server is.
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