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Regular Visitor
joltnjoe
Posts: 4
Registered: ‎07-01-2010

Can I set the Arris cable modem to bridged mode? (disable DHCP)

Hi.  I switched to Comcast two weeks ago.  I have an Arris telephony cable modem connected to a Linksys WRT54G wireless router.  Everything works great on my home network until I connect the ethernet port on my Motorola DCX3400 receiver onto my network... via a wired connection to my Linksys router.  When I do that... the PC's and other devices on my network can no longer connect to the internet.  (They get assigned an IP address from the cable modem instead of my Linksys router.)

 

I believe I need to disable the DHCP service on the Arris cable modem and set it to "bridged mode"... so that only the DHCP service on my Linksys router hands out IP addresses on my network.  (I did this previously with my DSL modem, and it worked great.)

 

So I have two questions:

 

1) Is there a way to disable the DHCP service on the Arris cable modem and put it into bridged mode?

 

2) I currently don't have my DCX3400 receiver connected to the network, and it seems to work fine.  As far as I could tell researching online, the ethernet port is not currently used for any features at this point?  Can someone confirm that is the case?

 

Thanks,
- Joe

Connection Expert
EG
Posts: 42,534
Registered: ‎12-24-2003

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

What is the exact model number of the Arris device ?

Regular Visitor
joltnjoe
Posts: 4
Registered: ‎07-01-2010

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

I have the Arris model TM602G/CT

Connection Expert
EG
Posts: 42,534
Registered: ‎12-24-2003

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

[ Edited ]

That device is a modem only. There is no router function, DHCP (if it has sync), or NAT being done by it. You may be inadvertently using the WRT54G as a switch. Do you have the WAN port of it connected to the modem and are you connecting your other devices to the LAN ports ?

Regular Visitor
joltnjoe
Posts: 4
Registered: ‎07-01-2010

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

Yes, I have the WAN port connected to the modem and the other devices connected to the LAN ports.

 

I did some more testing this morning.  Turns out if I only connect the DCX3400 receiver to the network, everything works fine.  The problem occurs when I connect my second RNG110 receiver to the network. 

 

When I connect the RNG110 to the network, then go to my PC and do an ipconfig release/renew... my PC picks up a 192.168.100.x IP address.  My Linksys router is configured to assign 192.168.2.x IP addresses.  If I disconnect the RNG110 and do another ipconfig release/renew... my PC picks up the correct IP address again.

 

Is there a way to adjust the network settings on the RNG110... or force it to reacquire an IP address?  I don't see anything in the user manual on this.  And the manual says the ethernet connection is for "future use"... so looks like I could just leave it disconnected.

Connection Expert
EG
Posts: 42,534
Registered: ‎12-24-2003

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

A write up on that device shows that the ethernet port is for "future use". I'm going to request that one of the cable T.V. experts check in to this thread and advise further.

Cable Expert
WarEagle57
Posts: 10,676
Registered: ‎12-31-2004

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

The ethernet port on the DCX3400 is not enabled.  The same is probably true of the RNG110.  I don't know anything about the Arris modem, or why he's trying to connect the cable TV boxes to it.  I suggest he quit what he's doing and restore the original configuration.

Connection Expert
EG
Posts: 42,534
Registered: ‎12-24-2003

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

Sounds like a plan !! Thanks for your feedback good sir !

Email Expert
Posts: 18,241
Registered: ‎04-27-2004

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

From his symptoms, my guess is that the RNG100 is acting as a DHCP server, and handing out an IP as if it were a cable modem. I suspect the RNG100 has a built-in cable modem, and that's what its Ethernet port is for. But the modem isn't provisioned, so it hands out a 192.168.100.x address.

Regular Visitor
joltnjoe
Posts: 4
Registered: ‎07-01-2010

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

OK thanks everyone for your help.  Sounds like the ethernet port is not currently used for anything on both the DCX3400 and RNG110 receivers.  So I'll just leave the ethernet port disconnected.

 

FYI the Comcast technician that installed my system connected the ethernet port.  Might be a good idea to let your folks in the field know that the ethernet port should just be left disconnected since it is not currently used... and in some cases can interfere with a customer's home network.

 

Thanks all!

Email Expert
Posts: 18,241
Registered: ‎04-27-2004

Re: Can I set the Arris cable modem to bridged mode? (disable DHCP)

Thanks, I've forwarded your note to the Comcast admins.