• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

Cable Modem --> Hub --> WAP?

D

Dooling37

Senior member
Hello --

I've just added a hub in between my cable modem (Motorola SB5100 from Comcast) and my WAP / 4-port switch (DLink Dl-614+). The hub is a brand-new, relatively cheap Netgear EN104TP. It's purpose is to (will be to) send all network traffic to a Linux system running a web server and Snort, a sort of DMZ system. This is to be the only system directly plugged into the hub; the other connection goes to the WAN port of the WAP. The WAP has filtering rules enabled.

Now, upon plugging in the power for the hub, it was receiving from the cable modem (on the uplink port, with a straight cable), as was the WAP. However, the Linux system's NIC could not be activated from the hub. Tried plugging a Windows system (which had been connected fine into the WAP switch) into this hub also, and it could not pull an IP either (DHCP unreachable). Out of curiousity, I turned the uplink port back into a regular port, and it was still receiving data and sending data to the WAP just fine; no difference with the two directly connected machines.

So, I've obviously done something wrong. Please help figure out what it is..? I'm thinking I probably have to buy an additional switch to live between the hub and cable modem, but God, I hope I'm wrong. I'm broke, and all out of power outlets. ; )

TIA!
 
amdfanboy -- So, the hub will not perform nat/dhcp to hide any systems behind it?

FishTaco -- I thought about doing that, but since the WAP acts as a switch, rather than a hub, the Linux machine would only see traffic destined specifically for it, I think, whereas I'd like it to see all traffic coming into my home network, for sniffing/IDS purposes..

Thanks.
 
Update -- actually, when I change the uplink port (which is connected to the cable modem with a straight cable) to a regular port, the local Windows system receives its own IP addy from comcast. (I had not restarted the modem previously, which is apparently why nothing changed). When I change it back to uplink, only the "downstream" connections (WAP and WAP-connected systems) work; the Windows system can no longer pull an addy from DHCP, once again.

Wow, I am confused.
 
Ok, first of all, I recommend you read more before you expose a computer to the internet 🙂

Try www.ezlan.net. They also have links to the basics.

I may be making a wrong assumption about your knowledge, and I apoligize if I'm wrong, but it just seems you're missing some of the basic concepts about TCP/IP, local and public IP address, DHCP, hubs, switches, routers, etc.

That being said, you could setup your linux box with a second nic as your firewall/ids/whatever and have it sit between the modem and your LAN. There are several free firewalls for linux out there, I suggest the firewall be your first priority then the IDS.
 
Thanks for the link, FishTaco.

I'm not as ignorant as I may sometimes seem from my posts here. I just lack common sense oftentimes. ; )

Anyhow, I see now that the hub will not perform NAT/DHCP for me. I think I will try as you suggested with a second NIC in the Linux box. I've done some messing around with IPTables, although if you have other suggestions, I'm open to them. The IDS/sniffing is just for educational purposes. I am not terribly concerned about anything on my network, and would not monitor the IDS religiously. Just want to see how one works in practice.

Thanks for your help..
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top