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New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011
Accepted Solution

Motorola sbg901 bridging mode

I am trying to use my own router with my motorola modem, but I am having some issues. This is what I've done:

 

1. Reset modem

2. Connect laptop to modem.

3. Disable NAPT by goign to setup->basic->NAPT mode-> disable  (I think now it is in bridging mode)

4. Reset ASUS router

5. Connect laptop to router

6. Change LAN IP to 192.168.0.1, keep everything else the same. WAN side is in DHCP mode. DHCP is enabled for the LAN side.

7. Connect router WAN side to the LAN port of the modem.

 

This is what I see:

 

1. Router recieved WAN DHCP lease

      IP:  98.233.253.234 /255.255.252.0

      Default route:   98.233.252.1

2. From PC, I can ping the router (192.168.0.1), but nothing in the internet side (8.8.8.8, 98.233.252.1)

2. From modem (accessed through 192.168.100.1), I can ping the router, but nothing else in the internet side.

 

I know I can either just use internal router in the motorola modem or plug in my router and live with double NAT, but I would rather not do that. Anyone have suggestions what I can try next? Thanks.

Networking Expert
Baric
Posts: 24,238
Registered: ‎07-28-2003

Re: Motorola sbg901 bridging mode

My advice is stop trying to run through hoops and ditch the sbg901 and get a plain cable modem, not like that combo router/modem.  I'd suggest a Motorola SB6120.

New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011

Re: Motorola sbg901 bridging mode

Funny you should say that. I had a plain old modem in my previous apartment. I cancelled comcast service and they insisted my modem belongs to them. Unless I gave it to them, they would charge me. Now I got a new one through comcast offers and this is what they gave me. So, yea, I would love to have the old one back but I am stuck with this new one.

Connection Expert
JamesR
Posts: 6,437
Registered: ‎09-29-2007

Re: Motorola sbg901 bridging mode

Don't think NAPT is the Same as NAT.

I think port translation has to do with gaming and disabling it does not get you into Bridge mode.

Here is a link to the User Guide.  You can probably do what you want to do.

 

http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBUQFjAA&url=http%3A%2F%2Fwww.csicable.com...

New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011

Re: Motorola sbg901 bridging mode

NAPT is just NAT with port translation.

Networking Expert
Baric
Posts: 24,238
Registered: ‎07-28-2003

Re: Motorola sbg901 bridging mode

The SBG901 is NOT a cable modem, it's a router/modem combo and should NOT be given out as a plain modem.  They usually give this device out to people who payed for the Home Networking service, or who took some kind of freebie/discount offer for a router.  Neither is a good deal, IMHO.  If the sbg901 is yours outright (freebie or bought from Comcast), just call Comcast and tell them you want to rent a regular cable modem.  Better yet, buy your own and save the rent you pay Comcast.  Either way, get rid of the SBG901.

 

If general, if they provided the modem, it belongs to them, you just rent it.  When you move or cancel your account, you have to return it, just like your cable settop box or remote, etc.  If you actually bought the modem, then make sure you keep the receipt to prove that.  If you replace their modem with your own, make sure you turn their modem back in (and get a receipt) or you can have trouble further down the line.

Connection Expert
JamesR
Posts: 6,437
Registered: ‎09-29-2007

Re: Motorola sbg901 bridging mode

No argument here, but If he owns the combo gateway then he could perhaps turn off the DhCP function and effectively turn it in to a bridge????

If he is renting it, he can trade it in for a regular modem.

 

New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011

Re: Motorola sbg901 bridging mode

I own the modem. It was a freebe from comcast offers.com.

 

If I turn off the DHCP on the modem and hook up a router to it, then I would essentially be double natting.  E.G.  public ip -> 192.168.0.x (motorola modem) -> 192.168.1.x (my router)  Some software have problems with double natting, plus I would have to port forward twice for services I want to expose. That is not the ideal case.

 

I spent all morning on this and I give up. I'm turning my two asus routers into switches and use them to connect to the motorola modem. Although I would rather have all the functionalities of ddwrt on the asus.  Thanks for the help.

Networking Expert
Baric
Posts: 24,238
Registered: ‎07-28-2003

Re: Motorola sbg901 bridging mode

Yes, it's technically possible and that's what he tried.  The fact that his Netgear router pulled a public IP from Comcast says it's talking out, but not very far.  That it works with the laptop direct connection but not the router indicates either a Netgear router issue, or possibly a compability issue with the router connected to the SBG901.  It's a funky setup that I would not recommend except as an experiment.

 

Now if the problem is in the Netgear router, swapping in plain cable modem won't work, but it's a quick thing to try since it's only $2 or so for the month for the modem.  Then he can either continue using the new modem, or get his own.

New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011

Re: Motorola sbg901 bridging mode

Are you using WEP with mac address filtering? If so, someone might be spoofing your device mac addresses and kicking you off.

New Visitor
xpan
Posts: 6
Registered: ‎04-23-2011

Re: Motorola sbg901 bridging mode

Thanks, Baric. Please ignore my previous post. It was meant for another thread.

 

I will hunt down a dedicated modem and try it. I'm sure it will work because I used the same setup in my previous apartment.

Connection Expert
EG
Posts: 44,212
Registered: ‎12-24-2003

Re: Motorola sbg901 bridging mode

FWIW, it is my understanding that the modem rental fee has now been increased to $5 - $7 bucks per month in most markets.

Networking Expert
Baric
Posts: 24,238
Registered: ‎07-28-2003

Re: Motorola sbg901 bridging mode

Yeah, my info is probably out of date, I haven't paid a rental fee on a modem in years.

Connection Expert
EG
Posts: 44,212
Registered: ‎12-24-2003

Re: Motorola sbg901 bridging mode

[ Edited ]

Me either.

Networking Expert
kevj
Posts: 4,859
Registered: ‎10-03-2003

Re: Motorola sbg901 bridging mode

Don't forget that with the sbg901 AND the netgear router in play, there are two routers involved, and potentially two hardware firewalls. The IP addresses that devices connected to the Netgear router will get are unknown to the motorola router, as the netgear router acts as their DHCP server. A static route will be required on the sbg901 to allow it to know where to forward return traffic from internet hosts. The Netgear router, when conncted to the sbg901, should get a DHCP supplied address on it's WAN port in the sbg901's LAN subnet range....unless these dual purpose devices work differently than a seperate router and modem setup.

 

It looks like you can disable the router/gateway function of the sbg901 in the Advanced Options page, by enabling Rg PassThrough. I believe this will allow you to use the unit as a modem only, and connect the Netgear router's WAN port to the LAN port on the sbg901, and get a public IP on the netgear, effectively putting the sbg901 in bridged mode...

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New Visitor
syeliset
Posts: 1
Registered: ‎06-26-2011

Re: Motorola sbg901 bridging mode

Thanks every1. That was very helpful. I also obtained a Motorola SBG-901 cable-modem + WiFi router combo device. I found this thread thru a google search for "SBG 901 modem only". I was trying to configure this newly obtained Motorola modem to work with my existing Linksys WiFi router that I use on LAN for wired & wireless access. So need that SBG901 to work as a cable modem only (disable router, DHCP, & NAT functionality).
With help from this thread, I was able to successfully do this as follows:
1) Connect Motorola SBG-901 Ethernet port to PC. Access gateway configuration page via browser at http://192.168.0.1 . Login, and change Advanced options :
Disable WAN blocking
Enable Rg PassThrough

Disable DHCP server functionality via the Options page ("No"). My Linksys router will handle DHCP
functionality.

Changed gateway IPAddress from default (192.168.0.1) to match the same subnet as Linksys router.

Disconnected Ethernet cable from PC, and connected from Modem to Linksys router's Internet port.

Ensured IP address assigned to modem is valid in the Linksys router's IP address range configuration.

Turned off both modem & router. Powered on the modem 1st. Waited a couple of minutes for it to go thru it reboot sequence. Then powered on the router. Verified via router's status page that it has been assigned the public WAN IP address.

Done!!
Connection Expert
JamesR
Posts: 6,437
Registered: ‎09-29-2007

Re: Motorola sbg901 bridging mode

Good Show, Way to Go

Thanks for posting your Step by Step.

Google will probably now show your post.:smileyhappy:

New Visitor
Flow_x
Posts: 1
Registered: ‎08-02-2011

Re: Motorola sbg901 bridging mode

This is really helpful. I did not do "Changed gateway IPAddress from default (192.168.0.1) to match the same subnet as Linksys router." because I do not quite understand how to get the subnet from the router, but everything still works perfectly! Btw, I am using D-Link N300. Hopefully it would be helpful for the people saw this thread later. =)

New Visitor
horaciop
Posts: 1
Registered: ‎09-06-2011

Re: Motorola sbg901 bridging mode

this post is very helpful, and i had to do some research the user and pass for the motorola page is user: admin, password: motorola, make sure you change it when logged in.  thanks for this post

New Visitor
oyee
Posts: 1
Registered: ‎09-29-2011

Re: Motorola sbg901 bridging mode

[ Edited ]

This apparently has become such a big issue that as of today, Comcast is including a special recorded message when you call tech support on how to fix it while you are waiting for a tech to answer :smileylaugh:

New Visitor
wirelessN
Posts: 1
Registered: ‎12-27-2011

Re: Motorola sbg901 bridging mode

Actually it is a lot simpler and I went a little more careful on the security bit.

 

Do not disable WAN blocking. Doing so will expose your internal network to the WAN and you really do not know who is out there looking at your stuff.

 

  1. I rest my SBG901 modem/router using a pin (refer modem manual).
  2. Connect to your modem/router using a cable and going to http://192.168.0.1
    • Default username and password are admin and motorola
  3. Change admin user password
  4. Go to page Basic -> DHCP and set DHCP to 'No'
  5. Go to page Basic -> Setup and set NATP to 'Disabled'
  6. Go to page Advanced -> Options and set the following:
    • WAN Blocking - Enabled
    • Ipsec PassThrough - Enabled (if you use IPSEC VPN connections)
    • PPTP PassThrough - Enabled (if you use PPTP VPN connections)
    • Remote Config Management - Disabled (unless you want to mange your gateway remotely - insecure)
    • Multicast Enable - Enabled
    • UPnP Enable - this will grey out after you set the next one.
    • Rg PassThrough - Enabled (this is what stops NAT. I got this from the Motorola Surfboard 901 manual. Download a PDF copy and sear for NAT and you will get it.)
  7. Connect your router. In my case I use an Apple Airport Extreme. I set the Internet connection to DHCP and restarted the modem. Make sure that you do not have drives connected and wait for about a minute before plugging in. Initially it was not taking the external router info from the modem but after persistence, I got it working.

Notice that I did not make a lot of changes. It migh look like a lot of settings but they are optional. You really need to stop DHCP, Disable NATP and Enable Rg PassThrough. Do not have to change the default IP either.

 

If you have diabled WAN Blocking - I recommend that you enable it immidiately. Be safe and be sure.

 

Happy Holidays.

New Visitor
Vagic
Posts: 1
Registered: ‎01-03-2012

Re: Motorola sbg901 bridging mode

Thank you. Hats off to the ifnormation... You guys saved me alot.

 

I was so worried that I paid so much money on the router (which worked well with ATT DSL Modem) and didnt work with this Comcast cable modem/router combo device.

Contributor
Blueflippy
Posts: 13
Registered: ‎02-08-2012

Re: Motorola sbg901 bridging mode

The Motorola SBG901 (modem with G wireless) can be connected with most wired/wireless N routers.  First, follow the directions provided by Comcast under their online Networking 101, called 'Things to Remember When Setting up or Changing Your Home Network.'  Comcast says in this article to release the IP configured for your Comcast Cable modem before trying to link a router.  Ultimately, what you end up with is two wireless systems running side-by-side: a G wireless and an N wireless, and, or course, your 4 wired ports available on the N router.  Yes, wireless devices in your home will 'see' both WIFI's - take your pick.  I am not an expert; I just did the relase first.