Re: Turning off DHCP in SB5120 in Motorola http://www.dslreports.com/forum/r15475092 en Sat, 05 Dec 2009 14:04:51 EDT Sat, 05 Dec 2009 14:04:51 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15604049 allyn : ok, i figured this out.

my sb5120 was still configured for nat and providing me with a private ip apparently because i had my router on and connected at the time it was configured by cox (i.e., the router was connected while the modem was still in unconfigured state).

i powered off the modem and router, powered the modem up and let it boot completely and then powered on the router. success! no more nat. the router acted as i thought it was supposed to and passed the public ip through to the router.

what a relief.

btw, what brilliant engineer chose orange for one of the status leds that will be on all the time (pc connectivity). in my opinion lights that are on all the time should be green. orange (or red) should be reserved for times when something is wrong... my other gripe with the sb5120 is the standby switch on the top. i'm worried it could get pressed accidentally...]]> http://www.dslreports.com/forum/remark,15604049 Fri, 03 Mar 2006 13:24:51 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15603797 allyn : i'm on cox hsi in san diego and just replaced a dead dlink dcm-201 cable modem with a surfboard sb5120. it appears that the modem itself is a nat device and has claimed the public ip address that my router used to have and has issued me a private address (192.168.100.2). i assume (but i haven't yet tested) that this will prevent incoming port forwarding since there is no way to configure port forwarding in the modem. i also see no way to disable the nat configuration in the modem.

did i buy the wrong modem? everything i read about the sb5120 was glowing.]]> http://www.dslreports.com/forum/remark,15603797 Fri, 03 Mar 2006 12:44:13 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15592108 DerEngel : A cable modem is a device with router characteristics (layer 3 OSI device), it is NOT a layer 2 device such as a network bridge. And if needed, I could support my claim, such as the fact that a DOCSIS cable modem uses IP addressing.

To answer 22bsti question, there is no way to change the gateway IP address (192.168.100.1) of a Surfboard modem, because its horribly hard coded in the firmware, it is however possible to change the HFC IP address (the dynamic one) using shell commands from within the modem.

And lastly, ISP's can block certain ports on a cable modem using LLC (Link Logic Control) filters. A filter can be applied in the configuration file by defining several SNMP objects. And of course, there are many ways to "undo" these types of filters. In fact, if you search the web, you may find a tutorial I wrote some time ago to do just that.]]> http://www.dslreports.com/forum/remark,15592108 Wed, 01 Mar 2006 21:56:07 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588948 Bror1 : well i was reading that it will get rid or my nat problems ive already forwarded the ports and all that but im still getting the message

this is what it essentially said

" The Motorola Surfboard cable modem is generally not a problem for port forwarding because it has no "router" functions in it.

However, apparently some ISPs have found a way to "remote configure" these modems to take advantage of a legitimate feature of the modem to BLOCK the ports needed for games and filesharing.


Normally a cable modem should just "pass along" everything that comes in over the cable connection, without modifying anything. But the Surfboard has a feature built-in which will provide "Private IP addresses" to all the computers connected to it if it detects the cable Internet connection has failed, or if the "Offline" button is pressed. This is to allow multiple computers on your local network to operate as a "LAN" without a connection to the Internet. It's a legitimate "safety feature" which most home users will never need. It appears however that the feature can be turned on remotely by reprogramming the modem over the Interenet connection from the ISP. This forces the modem to provide "Private IP addresses" even when connected to the Interent, and this interfers with the modem's ability to pass along the ports without blocking them..." ]]> http://www.dslreports.com/forum/remark,15588948 Wed, 01 Mar 2006 15:10:18 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588468 Johkal : You're not missing anything!

I guess like some people who would rather take their tires off the car every night as a theft deterrent. :uhh:
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Write me up for 125.......I Can't Drive 55 »redrocker.com/ »cabowabo.com/]]> http://www.dslreports.com/forum/remark,15588468 Wed, 01 Mar 2006 13:48:22 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588414 NoVA_CoxUser : While admittedly interesting ... I'm still at a loss as to WHY you'd want -- or need -- to disable it.

To my understanding -- and assuming that my earlier post is accurate -- as long as the modem's online, it's not issuing IPs anyway.

Or is there more to this story ???]]> http://www.dslreports.com/forum/remark,15588414 Wed, 01 Mar 2006 13:40:55 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588072 Johkal : I don't understand his instructions either. He'll post again sometime & probably detail it.
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Write me up for 125.......I Can't Drive 55 »redrocker.com/ »cabowabo.com/]]> http://www.dslreports.com/forum/remark,15588072 Wed, 01 Mar 2006 12:55:26 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588055 Bror1 : i still dont know what to do though help a complete noob out :D]]> http://www.dslreports.com/forum/remark,15588055 Wed, 01 Mar 2006 12:52:50 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15588043 Johkal : MIB: Management Information Base]]> http://www.dslreports.com/forum/remark,15588043 Wed, 01 Mar 2006 12:50:40 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15587984 Bror1 : I'm sorry but i don't understand how to do it. i don't know what the MIB is or any of that can someone tell me how to do it step by step i would really appreciate it :)]]> http://www.dslreports.com/forum/remark,15587984 Wed, 01 Mar 2006 12:42:05 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15566545 anon : well i figured out how to disable the dhcp server but i still dont know how to change the default lan ip address if anyone knows id be quite grateful]]> http://www.dslreports.com/forum/remark,15566545 Sun, 26 Feb 2006 16:31:11 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15566282 anon : DerEngel if you dont mind my asking how do you do this and i would like to change the default lan ip address as well(to 10.0.0.2 instead of 192.168.100.1 but thats not all that iportant)]]> http://www.dslreports.com/forum/remark,15566282 Sun, 26 Feb 2006 15:48:21 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15557114 DerEngel : ryan1012: It only says "DHCP Enabled" because you have to follow the instructions I posted earlier to unlock the secret feature to change it.]]> http://www.dslreports.com/forum/remark,15557114 Sat, 25 Feb 2006 02:54:44 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15523146 anon : I was reading this post and my Motorola modem has the 192.168.2.1/config.htm page but I don't have the ability to turn off the DHCP. It just says DHCP Enabled.

Also, I've been dropping my connection between my modem and my router. I just reciently baught a new Linksys Router that supports VPN and am very confident that it's not a router issue. But i've had this modem since about last August...

I've thought about just going out a buying a Linksys cable modem... Any thoughts on the Linksys vs. Motorola?
Click for full size
Screenshot
]]> http://www.dslreports.com/forum/remark,15523146 Mon, 20 Feb 2006 21:55:22 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15475092 still22loud : Thank you Nova for trying to explain things and thanks DerEngel for showing me that it is possible to turn DHCP off. You two are the best. ]]> http://www.dslreports.com/forum/remark,15475092 Tue, 14 Feb 2006 14:33:58 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15441189 DerEngel : Actually yes, you can turn off the modem's DHCP server. Motorola has this feature standard but it is hidden.

To do this, you need to enable the Factory MIB,
then using SNMP change the OID 1.3.6.1.4.1.1166.1.19.4.59.0 to integer 2, this enables a feature known "Read Only HTML". Finally, go to the modem's configuration page (»192.168.100.1/config.html) and you will now notice there is a check box next to "Enable DHCP Server", uncheck this box and click "Save".

Screenshot of the configuration page with hidden feature enabled:
»https://www.tcniso.net/shop/SB4200_UK_config.jpg]]> http://www.dslreports.com/forum/remark,15441189 Thu, 09 Feb 2006 18:33:28 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15367060 NoVA_CoxUser : Yes I know ... it's confusing.

Maybe it should say "enabled but offline" or maybe "enabled but not issuing IP addresses"]]> http://www.dslreports.com/forum/remark,15367060 Tue, 31 Jan 2006 00:48:04 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15366913 still22loud : Thanks for bearing with me, but I'm a little confused. When everything is up and running (modem, router, and internet), the configuration page on the Moto modem still say DHCP Server Enabled. ]]> http://www.dslreports.com/forum/remark,15366913 Tue, 31 Jan 2006 00:16:04 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15364437 NoVA_CoxUser : I don't think you understood ... as long as your modem is online ... it's DHCP server is disabled.

Your Linksys router's DHCP server will serve you just fine w/o any conflicts w/ the modem -- Moto modems are some of the best out there.]]> http://www.dslreports.com/forum/remark,15364437 Mon, 30 Jan 2006 19:06:06 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15364377 still22loud : Too bad I couldn't turn off the DHCP server on the modem. I really like using the DHCP server on the Linksys. Guess I have to call my cable company and tell them to give me another modem. Hope this is an option with Adelphia. Thanks Nova.]]> http://www.dslreports.com/forum/remark,15364377 Mon, 30 Jan 2006 19:00:07 EDT Re: Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15351684 NoVA_CoxUser : No need to disable a modem's DHCP server. (and no way to do it either w/o a hack)

The following is from the Moto SB5101 overview:
quote:
The SB5100 family of modems contain an internal DHCP server, which is active until the modem registers with the CMTS. In the case of a problem that prevents the modem from completing its registration, the modem can still give an IP address to the client PC to enable diagnostics access.

This address is given with a very short lease (around 10 seconds) so that as soon as the registration does complete the client PC obtains its proper IP address from the core network DHCP server.
]]> http://www.dslreports.com/forum/remark,15351684 Sat, 28 Jan 2006 21:15:42 EDT Turning off DHCP in SB5120 http://www.dslreports.com/forum/remark,15351516 still22loud : Hello everyone,

I was wondering if there is a way to turn off the DHCP server on the Motorola SB5120 Modem?

I have a Linksys router that will take care of the IP assignment already.

Thank you.]]> http://www.dslreports.com/forum/remark,15351516 Sat, 28 Jan 2006 20:47:56 EDT