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[Discuss] Changing Comcast Modem to Bridged
- Subject: [Discuss] Changing Comcast Modem to Bridged
- From: jbk at kjkelra.com (jbk)
- Date: Sun, 30 Dec 2018 12:05:33 -0500
- In-reply-to: <20181230154934.j3n4h2tmqvuw5ddr@randomstring.org>
- References: <6896ae06-58a9-ebca-121a-72fb8ad0ec29@kjkelra.com> <20181230154934.j3n4h2tmqvuw5ddr@randomstring.org>
On 12/30/18 10:49 AM, Dan Ritter wrote: > jbk wrote: >> A couple years ago we changed to comcast as our ISP and incorporated their >> modem into our network topology providing the dhcp, NAT and wireless >> functions. >> >> Prior to this we had a DSL modem and WRT54G running tomato. The modem >> provided dhcp so it was the gateway address. >> >> I now want to put the Comcast modem in bridge mode and have my wireless >> router running dd-wrt provide the dhcp and NAT for the wireless and wired >> LAN. >> >> According to the research I've done there are only two ip address options >> for setting up the modem in bridge mode. 10.0.0.1 or 192.168.100.1. >> >> My current network subnet mask is 255.0.0.0 for the dozen or so devices that >> have static IP's. I do not provide any services outside the local LAN but >> within I have a backup server that serves a number of devices. >> >> As I understand it the modem IP in bridged mode wants to be on a different >> subnet that the internal LAN which would lead me to believe that the 192 >> prefixed IP address would be the choice, this is question #1 >> >> Once I've setup the modem with the correct IP then will the router now >> become the gateway? >> >> I have the Cisco DPC3941T modem, has anyone on here set up the bridge >> themselves, I see the option in the management GUI, or per my web searching >> this change can only be done correctly by the right Comcast personel >> remotely? >> >> Well that's the gist of it, did I leave out anything? > You've got some confusion in there. Yes, I set this network up around 2001 with the help of someone else that new networking better than I. > > 1. NAT has to be handled by a router which has at least one > outside address and at least one inside address. /Which would now be my router in bridge mode./ > 2. DHCP can be done by any device on the inside. > > 3. A bridge operates at the ethernet level, not the IP level. > So once it's in operation, you pretend it's a chunk of wire: > your router connects to the bridge and uses the Comcast > assigned outside address(es), and connects to your internal > network with internal address(es). /So the router LAN address will now become the gateway address on my internal network?/ > A subnet mask indicates how large a chunk of the IP space should > be considered as local. You've got 16.7 million addresses > considered local right now... /Yes, I only learned this later after I had made all these other static decisions/ > The net says: > > Cisco DPC3941T modem > > 1) Press and hold reset button on back of gateway for 30 > seconds, this will reset the gateway back to the factory > defaults.. > > 2) Connect a computer to ethernet port #2 on the back of the > gateway. > > 3) After the gateway boots, verify computer has connectivity, > connect to gateway @ 10.0.0.1 > > 4) Change the gateway's login password, disable both private > wifi networks, set ipv4 and ipv6 firewall to custom mode and > select option disable/none. > > 5) Set Gateway > At a Glance > Bridge Mode to Enable. When you > see the timer screen pop up, you can disconnect the computer > from the gateway as it is rebooting. the reboot can take 3 - 5 > minutes. > > 6) Connect your router to the gateway ethernet port #1, on the > router make sure that the WAN / Internet link is set to disabled > or off. > > 7) Once the gateway completes it's boot cycle, enable the > Internet WAN on the router. The router should now have the IP > address issued by Comcast. > > 8) Configure the router as you see fit. > > Hope that helps. > > -dsr- > > Thanks Dan, I did see the instructions on the net of the steps you outline here, but out of context of my network. DD-WRT has a lot of helpful information on their site and forums and I am confident once the modem is in bridge mode I can implement a network more tailored to our needs including a VAP to get our frequent guests off our local LAN. Jim -- Jim Kelly-Rand jbk at kjkelra.com
- References:
- [Discuss] Changing Comcast Modem to Bridged
- From: jbk at kjkelra.com (jbk)
- [Discuss] Changing Comcast Modem to Bridged
- From: dsr at randomstring.org (Dan Ritter)
- [Discuss] Changing Comcast Modem to Bridged
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