C7000 Can not change LAN IP to 192.168.100.___

So here is the bottom line:

But the bigger issue is .... AND major drawback with at least this model Netgear cable modem/router (C7000) is that the engineers at Netgear decided to intentionally allocate ALL the addresses that start with the octet of 192.168.100.xxx to some other purpose which completely blocks them from being used at all by the end user.

It is a common practice for businesses to use 192.168.100.xxx as the IP octet for there static networks....... just like 192.168.1.xxx is usually used for Home based networks. This is not written in stone it just seems to be a common practice.... having supported hundreds of businesses over the years.

Other brand cable modem/routers do NOT design there devices so that 192.168.100.xxx are not available to the end user.

I sold this really nice C7000 on Craigslist for just a small loss and purchased a Linksys model which allowed me to use it on this business domain which has ALL of its devices using static IP’s starting with 192.168.100.xxx.

Up until this point I REALLY, REALLY liked Netgear devices.... they always worked (ie no flaws out of the box), are VERY user friendly and most importantly very compatible with other network equipment.

But thanks to this recent design change by Netgear I am going to have to rethink my preferences when purchasing cable modem/routers.

Interestingly enough SEVERAL of the “experts” at Netgear that replied to my support request knew NOTHING of this limitation with there cable modem/routers. If you go back to the very beginning of my post here .... you will see just how many “experts” at Netgear replied to my post and suggested possible “fixes” for something that can not be changed because it was intentionally designed that way by the engineers at Netgear.

tekman101101

it is NOT a flaw. It is by design.  

It is as per DOCSIS specification. Please review if you have time.

you have so many private subnets (as per RFC1918) to use and I am not sure why you are just stuck with 192.168.100.x. Also every "Cable Modem Router" should have the same design as well. you can purchase a non-NTGR modem and report back here if you see different behaviour. 

**FROM DOCSIS 3.0 OSSI Spec**

The CM MUST support 192.168.100.1, as the well-known diagnostic IP address accessible only from the CMCI interfaces. The CM MUST support the well-known diagnostic IP address, 192.168.100.1, on all physical interfaces associated with the CMCI. **** you can download the specification from CableLabs website. It is free. 

you could cross-reference this post on the DSLReports Forum where lot of esteemed Cable Community members post and they can provide you further details as well  (https://www.dslreports.com/forum/comcast)

> So here is the bottom line:
> [...]

   I know nothing, but it sounds to me as if the C7000 effectively
comprises a cable modem which has a LAN subnet of 192.168.100.0/24, and
a LAN interface address of 192.168.100.x, and a router whose WAN
interface (address 192.168.100.y, where y != x) is connected to the
modem's LAN interface.

   Because the (real, internal) router has a WAN interface on a
192.168.100.0/24 subnet, it can't allow a LAN address which uses that
same subnet.  Hence:

> "FAILURE Invalid data. LAN IP address overlapped"

The overlap would be between the proposed 192.168.100.0/24 LAN subnet
and the internal (hidden) 192.168.100.0/24 WAN subnet.

   I don't know if it's true, but it would seem to explain the observed
behavior.  It might also explain why pointing a web browser at
192.168.100.1 leads to the usual built-in web server which is normally
accessed at the router's LAN address.  (y = 1?)

> What I am saying is that Ip could be in use by the modem [...]

   Exactly.  Of course, documenting that restriction might have been
more helpful than not documenting it.  (And might have saved us all from
a series of rants.)

    To me, this sounds like a relatively clever (although inelegant)
engineering decision, allowing the reuse of some existing modem
hardware/firmware.  If the firmware allowed the user to change the
internal (hidden) subnet, or if the firmware could do it automatically,
then this limitation could be overcome.  I'd guess that the number of
users who actually care is probably too small to justify the effort.
But what do I know?

antinode

C7000 is rather a homogenous product and not two seperate products inside.

I am going to seperate different IP address into different stacks. exact terminology may be different but more on these lines. 

CM - Stack  = this is Management IPv4/IPv6 address which ISP such as Comcast uses to manage the Cable modem

WAN-Stack = This is ONLY on Cable Modem Routers/Gateways. this is true WAN address where all the traffic is NAT'ed. for most ISPs, you will get Public IPv4/IPv6 address here.

LAN - Stack =  this is your private address where the traffic is NAT'ed. Typically 192.168.0.x 

Private - Stack = This is the 192.168.100.1 stack which is listening for LAN side HTTP for diagnostics and GUI access. This is there on both Cable modems and Cable Modem Routers/Gateways. This interface does NOT NAT traffic.

> C7000 is rather a homogenous product and not two seperate products
> inside.

   Ah, well.  It was a good hypothesis while it lasted.  Thanks for the
(real) explanation.

I am not going to waste any more of my valuable time on this issue that turns out to be because of a poorly designed Netgear cable modem/router!

If this is so widely known as you are trying to say....... why didn’t several Netgear employees .... so called “experts” know about it? I submitted a support request to Netgear about this issue and at least SIX different “experts” tried to solve it BEFORE bumping it up to the next level of support.

As I mentioned in my previous reply I sold this unused Netgear C7000 on Craigslist for just a small loss.

AND ....I was able to purchase and use an Actiontec (sorry I mistakenly said it was a Linksys brand earlier) Cable modem router and I had NO TROUBLE setting it’s internal IP address to 192.168.100.254

I forget exactly what model Actiontec I purchased but I will get it the next time I am at this business and try to post it here.

I support hundreds of residential customers and dozens of small businesses here in the Portland, Oregon area...... and (as I mentioned previously) it is a common practice for businesses to use the first three octet’s of 192.168.100.xxx for there network devices AND to set up all there devices with static IP addresses.

I am certainly NOT going to change the static IP addresses on well over FIFTY network devices because Netgear has made a poor decision to block off all of the addresses where the first three octet’s are 192.168.100.xxx

I am VERY disappointed with Netgear right now and I am going to reconsider what brand network devices I purchase AND recommend to my customers going forward!

sure. Please post a model of the "actiontec" "Cable Modem Router" which you purchased. We would be happy to check it. 

as far I know, I have not seen actiontec manufacturing "Cable Modem Router" devices. It is not on their website (https://www.actiontec.com/wifi-routers-gateways/).