[Discuss] Changing Comcast Modem to Bridged

[jbk at kjkelra.com (jbk)]

On 12/30/18 11:01 AM, Robert Krawitz wrote:
> On Sun, 30 Dec 2018 10:39:06 -0500, 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.
> I've done that by the simple expedient of connecting our domestic
> router to our (RCN -- it doesn't matter) router, and having everything
> else except for my server system connect to our domestic router.  In
> other words, a DMZ topology.  The only thing I had to configure on the
> RCN router was the port forwarding to any ports I want open on the
> server.
>
> If you don't have a static IP/no open ports, it's even easier; the
> only two things on the DMZ are the ISP router and the domestic
> router.
>
The problem with doing that is there is no way to turn off 
the Comcast dhcp server w/o putting it into bridged mode, 
other than limiting the range to a single address and have 
that lease set to forever. But forever on the modem is only 
as long as that device remains connected without 
interruption. If there is an interruption, power outage, 
then the first device detected on resumption will get that 
address lease.

Thanks Robert, I would have to do a lot more research to see 
what setting up a DMZ would mean to my topology and the dhcp 
issue is the biggest headache and bridge mode is the only 
way to turn it off on the modem.

-- 
Jim Kelly-Rand
jbk at kjkelra.com