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Martin, System Administrator
Category: Networking
Satisfied Customers: 2933
Experience:  10+ Years Experience CCNA Network Engineer A+ Net+ Linux & Windows OS C++ Programming
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I have a Surfboard SB6180. When I connect it to a router,

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I have a Surfboard SB6180. When I connect it to a router, the downstream appliances get no internet. I get internet if I connect directly from the cable modem to my ethernet port on a laptop. But I've noticed that the cable modem is also giving out IP addresses to dozens of devices that are not on my network. Are they from neighbors? Is Cox showing me what's on my neighbors' connections? I can ping some of the devices. I'm worried about the security of this.

Hi, my name is ***** ***** I will do my best to help you today. To make sure I don't miss anything, please give me a minute to review your question.

May I know the model of the router?

I would try resetting the router first, to see if it's able to get an IP address from the modem - once that has been achieved you can set a password ***** the wireless network.

Customer: replied 4 months ago.
SB 6180. I'm not even working on the wifi. I just want my wired network to function. I have a switch downstream from the cablemodem. The Cox tech tells me that it won't do DHCP itself, which would explain the problem. Is that all it is?
Customer: replied 4 months ago.
I think I found my answer. Let's cancel this.

The problem is most probably DHCP related - but if your modem wasn't giving out a DHCP address, your computer wouldn't be able to connect directly either

Of course, you can connect directly to the router via ethernet and configure the LAN settings manually, with an IP address in the range of the modem's and set the default gateway as the modem's network IP

Customer: replied 4 months ago.
I don't see anything to configure the DHCP in the cable modem. If it just gave out DHCP automatically, that'd be fine. But it does all sorts of screwy things instead. I think I'll just park an old wifi router, with the wifi off, between the cable modem and the rest of the network.
Customer: replied 4 months ago.
Cox says that cable modem will only dispense ONE IP address.

The cable modem only has to dispense one IP address either way, to the router - the router can then give out a DHCP lease to the rest of the computers in your network

Customer: replied 4 months ago.
Right. I just don't have a router in that stream now. I thought I could just put it into a switch and it would pass on addresses. It did for a little while. I'm not sure why. But it quit. I think I'll just add a router.
Customer: replied 4 months ago.
I have to leave now, on an errand. I will be available again at around 4 pm—in about 90 minutes. Thanks.

It should do that with a switch or a router - but the switch/router needs to have DHCP enabled for the rest of the computers to get a connection to the modem.

Sure, no problem.

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Thank you

Martin and 3 other Networking Specialists are ready to help you
Customer: replied 4 months ago.
Thank you!