Timeline for answer to Advice for network & device configuration using Comcast Modem? by Ron Maupin
Current License: CC BY-SA 3.0
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| when toggle format | what | by | license | comment | |
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| Nov 18, 2015 at 19:36 | comment | added | Ron Maupin♦ | Right, and you can get your own modem, but you want that public address on your router. To do that, you will need to work with Comcast. There is nothing you can configure on your router or network to get that address if the Comcast modem is going to claim it. | |
| Nov 18, 2015 at 19:08 | comment | added | Andrew Philips | I really get how DHCP and Static IP work at the ISP level and internal to my network. I realize that you think I'm confused. However, there is a third more complex thing happening here, as I've seen the Modem in this config during Bridging: Modem WAN DHCP client addr assigned from Comcast (50.161.X.X), Modem reachable from LAN side via 10.0.0.1 address, no LAN side services (DHCP Server, NAT, fw) working. That's not a true Bridge Mode, it's still acting like a Router, just with services turned off. A DHCP client on Modem LAN side cannot "see" Comcast DHCP server, hence, laptop was link local. | |
| Nov 18, 2015 at 18:57 | comment | added | Ron Maupin♦ | If you need the VPN on the router, the router needs the public IP address. Either you have a static, public IP address assigned by Comcast, or you get it from Comcast via DHCP. This is a problem you have with Comcast. | |
| Nov 18, 2015 at 18:53 | comment | added | Andrew Philips | Thanks, but I need to run VPN into the Router, so the Router (and not the Modem) needs its external face available. Thanks. You moved my understanding a bit further down the road. I'm not sure I fully understand, yet. If I see other answers here or when I finally get it working, I will post something. | |
| Nov 18, 2015 at 18:50 | comment | added | Ron Maupin♦ | What I have explained a couple of times is that you have two choices for your router WAN configuration: a static address assigned by Comcast, or DHCP. Those are your two choices. You can work with Comcast to determine the appropriate choice. This is really very simple, and people do this everyday. You wanted this from someone who does this, and I do this. If you want to eliminate the modem as a network device, you can set it to bridge mode, or you can get your own. I really don't understand the problem. If it works, there is no real reason to change it since you don't gain anything tangible. | |
| Nov 18, 2015 at 18:44 | comment | added | Andrew Philips | I'm not asking about the Modem connection to the ISP, I'm asking about the Router connection to the Modem in Bridge Mode. In that mode, DHCP client requests are not handled. Furthermore, in Bridge Mode, the Modem itself has a WAN assigned IP (provisioned by DHCP) and a LAN reachable IP, therefore my Router cannot request anything as a DHCP client. From this discussion, I'm guessing I really need to make a static IP assignment on the Router WAN Port and test with Modem Bridging. | |
| Nov 18, 2015 at 18:36 | comment | added | Ron Maupin♦ | If the laptop worked when it was set to DHCP, that's what you need to do for your router. Do You have an assigned, static, public IP address from Comcast? If so, you use that, if not, you must use DHCP. Questions from end-users of ISPs are specifically off-topic, so you will need to deal with Comcast about that. This is really pretty easy, you either have an assigned public IP address which you must use, or you connect via DHCP. | |
| Nov 18, 2015 at 18:32 | comment | added | Andrew Philips |
Actually, the laptop didn't get its address from DHCP. It set its address to a link local address 169.254.X.X. I'm suspecting the reason this works for you is that the Modem gives you a proper Bridge Mode and you pick up the DHCP Server from your cable provider. Whereas, the less than true Bridge Mode on my modem means I need to set that Port as a static IP. I really do believe the remainder of my internal network is configured just fine. A show xxx on the Router for arp, dhcp bindings, nat, etc. has everything you'd expect. I'm not relying on Modem for anything but WAN access.
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| Nov 18, 2015 at 18:22 | history | answered | Ron Maupin♦ | CC BY-SA 3.0 |